Output Font Incorrectly Configured

[mustaqimM]

In my fonts/iosevka folder, I have 24 fonts:

iosevka-bold.ttf              iosevka-bolditalic.ttf   iosevka-boldoblique.ttf       iosevka-extrabold.ttf          iosevka-extrabolditalic.ttf
iosevka-extraboldoblique.ttf  iosevka-extralight.ttf   iosevka-extralightitalic.ttf  iosevka-extralightoblique.ttf  iosevka-italic.ttf
iosevka-light.ttf             iosevka-lightitalic.ttf  iosevka-lightoblique.ttf      iosevka-medium.ttf             iosevka-mediumitalic.ttf
iosevka-mediumoblique.ttf     iosevka-oblique.ttf      iosevka-regular.ttf           iosevka-semibold.ttf           iosevka-semibolditalic.ttf
iosevka-semiboldoblique.ttf   iosevka-thin.ttf         iosevka-thinitalic.ttf        iosevka-thinoblique.ttf        

But when I run make, I get 17 fonts:

LigaIosevka-Bold.ttf                LigaIosevkaExtraboldOblique-Extrabold.ttf    LigaIosevkaMedium-Medium.ttf             LigaIosevkaThin-Thin.ttf
LigaIosevka-Italic.ttf              LigaIosevkaExtralight-Extralight.ttf         LigaIosevkaMediumOblique-Medium.ttf      LigaIosevkaThinOblique-Thin.ttf
LigaIosevka.ttf                     LigaIosevkaExtralightOblique-Extralight.ttf  LigaIosevkaOblique-Oblique.ttf           
LigaIosevkaBoldOblique-Bold.ttf     LigaIosevkaLight-Light.ttf                   LigaIosevkaSemibold-Semibold.ttf         
LigaIosevkaExtrabold-Extrabold.ttf  LigaIosevkaLightOblique-Light.ttf            LigaIosevkaSemiboldOblique-Semibold.ttf 

This is the output:

~> make
fontforge -lang=py -script build.py 2>&1 \
| fgrep -v 'This contextual rule applies no lookups.' \
| fgrep -v 'Bad device table'
Copyright (c) 2000-2014 by George Williams. See AUTHORS for Contributors.
 License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
 with many parts BSD <http://fontforge.org/license.html>. Please read LICENSE.
 Based on sources from 17:38 UTC 13-Oct-2018-ML-D.
 Based on source from git with hash: 
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Warning: Mac string is a subset of the Windows string in the 'name' table
  for the Family string in the English (US) language.
Warning: Mac and Windows entries in the 'name' table differ for the
  Styles (SubFamily) string in the language English (US)
  Mac String: Medium
  Windows String: Regular
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Warning: Mac string is a subset of the Windows string in the 'name' table
  for the Family string in the English (US) language.
Warning: Mac and Windows entries in the 'name' table differ for the
  Styles (SubFamily) string in the language English (US)
  Mac String: Light
  Windows String: Regular
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Ligaturizing font iosevka-bold.ttf (Iosevka) as 'Liga Iosevka'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Bold.otf
    ...saving to 'fonts/output/LigaIosevka-Bold.ttf' (Liga Iosevka Bold)
Ligaturizing font iosevka-regular.ttf (Iosevka) as 'Liga Iosevka'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Regular.otf
    ...saving to 'fonts/output/LigaIosevka.ttf' (Liga Iosevka)
Ligaturizing font iosevka-medium.ttf (Iosevka Medium) as 'Liga Iosevka Medium'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Medium.otf
    ...saving to 'fonts/output/LigaIosevkaMedium-Medium.ttf' (Liga Iosevka Medium Medium)
Ligaturizing font iosevka-thin.ttf (Iosevka Thin) as 'Liga Iosevka Thin'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Regular.otf
    ...saving to 'fonts/output/LigaIosevkaThin-Thin.ttf' (Liga Iosevka Thin Thin)
Ligaturizing font iosevka-semibolditalic.ttf (Iosevka Semibold) as 'Liga Iosevka Semibold'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Regular.otf
    ...saving to 'fonts/output/LigaIosevkaSemibold-Semibold.ttf' (Liga Iosevka Semibold Semibold)
Ligaturizing font iosevka-extrabold.ttf (Iosevka Extrabold) as 'Liga Iosevka Extrabold'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Regular.otf
    ...saving to 'fonts/output/LigaIosevkaExtrabold-Extrabold.ttf' (Liga Iosevka Extrabold Extrabold)
Ligaturizing font iosevka-boldoblique.ttf (Iosevka Bold Oblique) as 'Liga Iosevka Bold Oblique'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Bold.otf
    ...saving to 'fonts/output/LigaIosevkaBoldOblique-Bold.ttf' (Liga Iosevka Bold Oblique Bold)
Ligaturizing font iosevka-bolditalic.ttf (Iosevka) as 'Liga Iosevka'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Bold.otf
    ...saving to 'fonts/output/LigaIosevka-Bold.ttf' (Liga Iosevka Bold)
Ligaturizing font iosevka-lightoblique.ttf (Iosevka Light Oblique) as 'Liga Iosevka Light Oblique'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Regular.otf
    ...saving to 'fonts/output/LigaIosevkaLightOblique-Light.ttf' (Liga Iosevka Light Oblique Light)
Ligaturizing font iosevka-light.ttf (Iosevka Light) as 'Liga Iosevka Light'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Light.otf
    ...saving to 'fonts/output/LigaIosevkaLight-Light.ttf' (Liga Iosevka Light Light)
Ligaturizing font iosevka-mediumitalic.ttf (Iosevka Medium) as 'Liga Iosevka Medium'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Regular.otf
    ...saving to 'fonts/output/LigaIosevkaMedium-Medium.ttf' (Liga Iosevka Medium Medium)
Ligaturizing font iosevka-extralight.ttf (Iosevka Extralight) as 'Liga Iosevka Extralight'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Regular.otf
    ...saving to 'fonts/output/LigaIosevkaExtralight-Extralight.ttf' (Liga Iosevka Extralight Extralight)
Ligaturizing font iosevka-extralightoblique.ttf (Iosevka Extralight Oblique) as 'Liga Iosevka Extralight Oblique'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Regular.otf
    ...saving to 'fonts/output/LigaIosevkaExtralightOblique-Extralight.ttf' (Liga Iosevka Extralight Oblique Extralight)
Ligaturizing font iosevka-extralightitalic.ttf (Iosevka Extralight) as 'Liga Iosevka Extralight'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Regular.otf
    ...saving to 'fonts/output/LigaIosevkaExtralight-Extralight.ttf' (Liga Iosevka Extralight Extralight)
Ligaturizing font iosevka-semibold.ttf (Iosevka Semibold) as 'Liga Iosevka Semibold'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Regular.otf
    ...saving to 'fonts/output/LigaIosevkaSemibold-Semibold.ttf' (Liga Iosevka Semibold Semibold)
Ligaturizing font iosevka-lightitalic.ttf (Iosevka Light) as 'Liga Iosevka Light'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Regular.otf
    ...saving to 'fonts/output/LigaIosevkaLight-Light.ttf' (Liga Iosevka Light Light)
Ligaturizing font iosevka-thinitalic.ttf (Iosevka Thin) as 'Liga Iosevka Thin'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Regular.otf
    ...savingLookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
Lookup 'mark' Mark Positioning lookup 0 has an
  offset bigger than 65535 bytes. This means
  FontForge must use an extension lookup to output it.
  Not all applications support extension lookups.
 to 'fonts/output/LigaIosevkaThin-Thin.ttf' (Liga Iosevka Thin Thin)
Ligaturizing font iosevka-extraboldoblique.ttf (Iosevka Extrabold Oblique) as 'Liga Iosevka Extrabold Oblique'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Regular.otf
    ...saving to 'fonts/output/LigaIosevkaExtraboldOblique-Extrabold.ttf' (Liga Iosevka Extrabold Oblique Extrabold)
Ligaturizing font iosevka-mediumoblique.ttf (Iosevka Medium Oblique) as 'Liga Iosevka Medium Oblique'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Regular.otf
    ...saving to 'fonts/output/LigaIosevkaMediumOblique-Medium.ttf' (Liga Iosevka Medium Oblique Medium)
Ligaturizing font iosevka-semiboldoblique.ttf (Iosevka Semibold Oblique) as 'Liga Iosevka Semibold Oblique'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Regular.otf
    ...saving to 'fonts/output/LigaIosevkaSemiboldOblique-Semibold.ttf' (Liga Iosevka Semibold Oblique Semibold)
Ligaturizing font iosevka-italic.ttf (Iosevka) as 'Liga Iosevka'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Regular.otf
    ...saving to 'fonts/output/LigaIosevka-Italic.ttf' (Liga Iosevka Italic)
Ligaturizing font iosevka-oblique.ttf (Iosevka Oblique) as 'Liga Iosevka Oblique'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Regular.otf
    ...saving to 'fonts/output/LigaIosevkaOblique-Oblique.ttf' (Liga Iosevka Oblique Oblique)
Ligaturizing font iosevka-thinoblique.ttf (Iosevka Thin Oblique) as 'Liga Iosevka Thin Oblique'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Regular.otf
    ...saving to 'fonts/output/LigaIosevkaThinOblique-Thin.ttf' (Liga Iosevka Thin Oblique Thin)
Ligaturizing font iosevka-extrabolditalic.ttf (Iosevka Extrabold) as 'Liga Iosevka Extrabold'
    ...using ligatures from fonts/fira/distr/otf/FiraCode-Regular.otf
    ...saving to 'fonts/output/LigaIosevkaExtrabold-Extrabold.ttf' (Liga Iosevka Extrabold Extrabold)

Also I when I use the Medium weight, it's now only in Italic(The name also show as Liga Iosevka Medium Medium)
The only font that works correctly is the regular one. The rest act as Italic

[ToxicFrog]

Based on the output names (e.g. LigaIosevkaExtralight-Extralight.ttf) I'd guess that the code that tries to figure out which part of the font name is the actual name and which part is the weight is getting confused.