harfbuzz: Remove cairo dependency

Upstream recommends cairo, but it is only used for development
purposes and is not part of the library.
This removes transitive (build) dependencies on various X11 or
other GUI-related libraries, which is desirable for minimizing
rebuilds and maximizing parallellism.

This also adds fontconfig to buildInputs, because this direct lib
dependency was previously found via cairo's propagatedBuildInputs.

pkgs/development/libraries/harfbuzz/default.nix

@@ -4,7 +4,7 @@
 , pkg-config
 , glib
 , freetype
-, cairo
+, fontconfig
 , libintl
 , meson
 , ninja
@@ -57,6 +57,11 @@ stdenv.mkDerivation {
     (mesonFeatureFlag "graphite" withGraphite2)
     (mesonFeatureFlag "icu" withIcu)
     (mesonFeatureFlag "coretext" withCoreText)
+    # upstream recommends cairo, but it is only used for development purposes
+    # and is not part of the library.
+    # Cairo causes transitive (build) dependencies on various X11 or other
+    # GUI-related libraries, so it shouldn't be re-added lightly.
+    (mesonFeatureFlag "cairo" false)
     (mesonFeatureFlag "introspection" isNativeCompilation)
   ];
 
@@ -72,7 +77,7 @@ stdenv.mkDerivation {
     docbook_xml_dtd_43
   ];
 
-  buildInputs = [ glib freetype cairo ] # recommended by upstream
+  buildInputs = [ glib freetype fontconfig ]
     ++ lib.optionals withCoreText [ ApplicationServices CoreText ]
     ++ lib.optionals isNativeCompilation [ gobject-introspection ];