Build system: default to fmt shared library when available

[mazes-80]

Detect system libfmt, with minimal version 5.3.
I don't know if minimal version is required, but as it is the one found in externals ...

Oops, just noticed there's a new version of fmtlib (6.0.0)...

[leoetlino]

Since fmtlib 6.0.0 -- which contains backward-compatibility breaking changes -- has been released, and distros will be moving to 6.0.0 in the future, could you bump the requirement to 6.0.0 and update the copy in Externals please? Otherwise Dolphin will stop building at some point with this change...

[orbea]

A lot of distros already provide 6.0.0.

https://repology.org/project/fmt/versions

[mazes-80]

I updated fmt from External, everything seems compiles fine, no breaking changes detected yet !
The switch works well as my system fmt is 5.3, build system used 6.0.0 from "static"

[leoetlino]

Hmm, it's weird that everything still builds fine because fmt/time.h was removed in 6.0, and Core (IIRC) includes it.

[BhaaLseN]

The functionality is still there, but I can't find where we use it (nor in which PR I mentioned this before).
I mean, as long as it works...

[leoetlino]

Looks like the PR is based on an old-ish commit. Please rebase and fix the build issues that will most likely appear after doing so. (I think the only change you have to make is replace fmt/time.h with fmt/chrono.h.)

comments addressed

[leoetlino]

Looks like fmt 6.0.0 introduces a lot of new warnings (fmtlib/fmt#1278). Maybe we should consider disabling warnings for fmt (or even Externals in general)?

[orbea]

FWIW fmt upstream is now at 6.1.2, this PR still being worked on?

[mazes-80]

FWIW fmt upstream is now at 6.1.2, this PR still being worked on?

For now using fmt 6.1.2 from system fails to compile:
Source/Core/VideoCommon/BPStructs.cpp:992:55: error: cannot bind bitfield 'left_top.X10Y10::.X10Y10::::x' to 'unsigned int&'
Source/Core/VideoCommon/BPStructs.cpp:1186:77: error: cannot bind bitfield 'teximg.TexImage0::.TexImage0::::format' to 'unsigned int&'
Source/Core/VideoCommon/BPStructs.cpp:1209:40: error: cannot bind bitfield 'teximg.TexImage1::.TexImage1::::tmem_even' to 'unsigned int&'
Source/Core/VideoCommon/BPStructs.cpp:1232:40: error: cannot bind bitfield 'teximg.TexImage2::.TexImage2::::tmem_odd' to 'unsigned int&'

Locally I just add a '+ 0' to all those complaining bitfields, it works, but I'm sure it is not the proper way to cast. What would be the good way to cast ?

[leoetlino]

Apparently this is a known issue with 6.0+. The recommended workaround is to use the unary plus operator:

fmtlib/fmt#1284 (comment)

[mazes-80]

Apparently this is a known issue with 6.0+. The recommended workaround is to use the unary plus operator.

Pushed fmt 6.1.2, added unary plus were they were missing.

[orbea]

@mazes-80 I don't see the new commits?

[orbea]

Fwiw this builds here.

$  ldd /usr/games/dolphin-emu | grep -i fmt
	libfmt.so.6 => /usr/lib64/libfmt.so.6 (0x00007feed2d98000)

[leoetlino]

Apologies for the long delay... I've rebased your branch and removed some (now) unnecessary commits (considering #8602 was merged meanwhile). Thanks for your contribution!