lilypond: adjust fontconfig on macOS

{ stdenv, lib, fetchurl, ghostscript, gyre-fonts, texinfo, imagemagick, texi2html, guile

, python3, gettext, flex, perl, bison, pkg-config, autoreconfHook, dblatex

, fontconfig, freetype, pango, fontforge, help2man, zip, netpbm, groff

, freefont_ttf, makeFontsConf

, makeWrapper, t1utils, boehmgc, rsync

, texlive, tex ? texlive.combine {

    inherit (texlive) scheme-small lh metafont epsf fontinst;

    maintainers = with maintainers; [ marcweber yurrriq ];

    platforms = platforms.all;

  };

  FONTCONFIG_FILE = lib.optional stdenv.isDarwin (makeFontsConf {

    fontDirectories = [ freefont_ttf ];

  });

}