Revert "fontconfig: Only read versioned config dirs"

This reverts commit edf2541f02.

Turns out lot of software (including Chromium) use bundled fontconfig
so we either need to wrap every one of those, or re-introduce the global
unversioned config. The latter is easier but weakens hermetic configs.

But perhaps those are not really worth the effort. Given that programs
linked against fc 2.12.6 on fc 2.13.92 system seem to at least display text,
even while printing tons of errors (as long as you generate fc cache manually),
and same thing the other way around, hopefully it will not be an issue in the future.

We give up on the hermetic configs in exchange for getting rid of lot of complexity.

pkgs/development/libraries/fontconfig/default.nix

@@ -13,10 +13,9 @@
 
 /** Font configuration scheme
  - ./config-compat.patch makes fontconfig try the following root configs, in order:
-    $FONTCONFIG_FILE, /etc/fonts/${configVersion}/fonts.conf, ${fontconfig.out}/etc/fonts/fonts.conf
+    $FONTCONFIG_FILE, /etc/fonts/${configVersion}/fonts.conf, /etc/fonts/fonts.conf
     This is done not to override config of pre-2.11 versions (which just blow up)
-    and still use *global* font configuration at NixOS,
-    falling back to upstream defaults on non-NixOS.
+    and still use *global* font configuration at both NixOS or non-NixOS.
  - NixOS creates /etc/fonts/${configVersion}/fonts.conf link to $out/etc/fonts/fonts.conf,
     and other modifications should go to /etc/fonts/${configVersion}/conf.d
  - See ./make-fonts-conf.xsl for config details.
@@ -112,20 +111,11 @@ stdenv.mkDerivation rec {
   postInstall = ''
     cd "$out/etc/fonts"
     xsltproc --stringparam fontDirectories "${dejavu_fonts.minimal}" \
-      --stringparam fontconfig "$out" \
       --stringparam fontconfigConfigVersion "${configVersion}" \
       --path $out/share/xml/fontconfig \
       ${./make-fonts-conf.xsl} $out/etc/fonts/fonts.conf \
       > fonts.conf.tmp
     mv fonts.conf.tmp $out/etc/fonts/fonts.conf
-
-    # Make it easier to remove user config in NixOS module.
-    mkdir -p $out/etc/fonts/conf.d.bak
-    mv $out/etc/fonts/conf.d/50-user.conf $out/etc/fonts/conf.d.bak
-
-    # update latest 51-local.conf path to look at the latest local.conf
-    substituteInPlace $out/etc/fonts/conf.d/51-local.conf \
-      --replace local.conf /etc/fonts/${configVersion}/local.conf
   '';
 
   passthru = {