darwin: fix gtk+3 dependencies

pkgs/development/libraries/epoxy/default.nix

@@ -16,6 +16,11 @@ stdenv.mkDerivation rec {
   nativeBuildInputs = [ autoreconfHook pkgconfig utilmacros python ];
   buildInputs = [ mesa libX11 ];
 
+  preConfigure = stdenv.lib.optional stdenv.isDarwin ''
+    substituteInPlace configure --replace build_glx=no build_glx=yes
+    substituteInPlace src/dispatch_common.h --replace "PLATFORM_HAS_GLX 0" "PLATFORM_HAS_GLX 1"
+  '';
+
   meta = with stdenv.lib; {
     description = "A library for handling OpenGL function pointer management";
     homepage = https://github.com/anholt/libepoxy;

pkgs/top-level/all-packages.nix

@@ -6331,7 +6331,11 @@ let
 
   gettext = callPackage ../development/libraries/gettext { };
 
-  gettextWithExpat = callPackage ../development/libraries/gettext/expat.nix { };
+  gettextWithExpat = if stdenv.isDarwin
+    then gettext.overrideDerivation (drv: {
+      configureFlags = drv.configureFlags ++ [ "--with-libexpat-prefix=${expat}" ];
+    })
+    else callPackage ../development/libraries/gettext/expat.nix { };
 
   gd = callPackage ../development/libraries/gd { };