Enable Chez Scheme on Darwin

[eraserhd]

Motivation for this change

I want Chez on my dev laptop!

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option build-use-sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.

---

This change should have no effect on non-Darwin platforms. The comments in libiconv's expression and epic5 suggest this is the right handling for libiconv. But hey, this is my first PR, so, you know...

[globin]

@GrahamcOfBorg build chez

[GrahamcOfBorg]

Success for system: x86_64-linux

post-installation fixup
shrinking RPATHs of ELF executables and libraries in /nix/store/hha9pyz1h6q4w46iw2wwx4701rjifv26-chez-scheme-9.5-20171109
shrinking /nix/store/hha9pyz1h6q4w46iw2wwx4701rjifv26-chez-scheme-9.5-20171109/bin/petite
shrinking /nix/store/hha9pyz1h6q4w46iw2wwx4701rjifv26-chez-scheme-9.5-20171109/bin/scheme-script
shrinking /nix/store/hha9pyz1h6q4w46iw2wwx4701rjifv26-chez-scheme-9.5-20171109/bin/scheme
gzipping man pages under /nix/store/hha9pyz1h6q4w46iw2wwx4701rjifv26-chez-scheme-9.5-20171109/share/man/
stripping (with flags -S) in /nix/store/hha9pyz1h6q4w46iw2wwx4701rjifv26-chez-scheme-9.5-20171109/lib  /nix/store/hha9pyz1h6q4w46iw2wwx4701rjifv26-chez-scheme-9.5-20171109/bin 
patching script interpreter paths in /nix/store/hha9pyz1h6q4w46iw2wwx4701rjifv26-chez-scheme-9.5-20171109
checking for references to /tmp/nix-build-chez-scheme-9.5-20171109.drv-0 in /nix/store/hha9pyz1h6q4w46iw2wwx4701rjifv26-chez-scheme-9.5-20171109...
/nix/store/hha9pyz1h6q4w46iw2wwx4701rjifv26-chez-scheme-9.5-20171109

[GrahamcOfBorg]

Failure for system: x86_64-darwin

these derivations will be built:
  /nix/store/02iy5ccnj9nyazda7x2pck4ciqf9lddl-chez-scheme-9.5-20171109.drv
these paths will be fetched (26.76 MiB download, 48.90 MiB unpacked):
  /nix/store/0x45qzbcdsrhjygm2ll68krlcikz609p-chezscheme-bc117fd
copying path '/nix/store/0x45qzbcdsrhjygm2ll68krlcikz609p-chezscheme-bc117fd' from 'https://cache.nixos.org'...
error: a 'x86_64-darwin' is required to build '/nix/store/02iy5ccnj9nyazda7x2pck4ciqf9lddl-chez-scheme-9.5-20171109.drv', but I am a 'x86_64-linux'

[orivej]

I have replaced system /usr/bin/libtool with libtool from cctools.

[LnL7]

@GrahamcOfBorg build chez

[GrahamcOfBorg]

Success for system: x86_64-linux

post-installation fixup
shrinking RPATHs of ELF executables and libraries in /nix/store/jp6hddw3rv1amwg4262niyas93k1hyd3-chez-scheme-9.5-20171109
shrinking /nix/store/jp6hddw3rv1amwg4262niyas93k1hyd3-chez-scheme-9.5-20171109/bin/petite
shrinking /nix/store/jp6hddw3rv1amwg4262niyas93k1hyd3-chez-scheme-9.5-20171109/bin/scheme-script
shrinking /nix/store/jp6hddw3rv1amwg4262niyas93k1hyd3-chez-scheme-9.5-20171109/bin/scheme
gzipping man pages under /nix/store/jp6hddw3rv1amwg4262niyas93k1hyd3-chez-scheme-9.5-20171109/share/man/
stripping (with flags -S) in /nix/store/jp6hddw3rv1amwg4262niyas93k1hyd3-chez-scheme-9.5-20171109/lib  /nix/store/jp6hddw3rv1amwg4262niyas93k1hyd3-chez-scheme-9.5-20171109/bin 
patching script interpreter paths in /nix/store/jp6hddw3rv1amwg4262niyas93k1hyd3-chez-scheme-9.5-20171109
checking for references to /tmp/nix-build-chez-scheme-9.5-20171109.drv-0 in /nix/store/jp6hddw3rv1amwg4262niyas93k1hyd3-chez-scheme-9.5-20171109...
/nix/store/jp6hddw3rv1amwg4262niyas93k1hyd3-chez-scheme-9.5-20171109

[GrahamcOfBorg]

Success for system: x86_64-darwin

if [ yes = yes ] ; then gzip -f /nix/store/dqjv5846kdfrfb5zdcdqbsiw401fgmhr-chez-scheme-9.5-20171109/share/man/man1/petite.1 ; fi
./installsh -o "" -g "" -d -m 755 /nix/store/dqjv5846kdfrfb5zdcdqbsiw401fgmhr-chez-scheme-9.5-20171109/lib/csv9.5.1/examples
./installsh -o "" -g "" -m 444 ../examples/* /nix/store/dqjv5846kdfrfb5zdcdqbsiw401fgmhr-chez-scheme-9.5-20171109/lib/csv9.5.1/examples
post-installation fixup
gzipping man pages under /nix/store/dqjv5846kdfrfb5zdcdqbsiw401fgmhr-chez-scheme-9.5-20171109/share/man/
stripping (with flags -S) in /nix/store/dqjv5846kdfrfb5zdcdqbsiw401fgmhr-chez-scheme-9.5-20171109/lib  /nix/store/dqjv5846kdfrfb5zdcdqbsiw401fgmhr-chez-scheme-9.5-20171109/bin
patching script interpreter paths in /nix/store/dqjv5846kdfrfb5zdcdqbsiw401fgmhr-chez-scheme-9.5-20171109
copying 1 paths...
copying path '/nix/store/dqjv5846kdfrfb5zdcdqbsiw401fgmhr-chez-scheme-9.5-20171109' from 'ssh://mac1'...
/nix/store/dqjv5846kdfrfb5zdcdqbsiw401fgmhr-chez-scheme-9.5-20171109