libepoxy: fix x11 support on darwin

pkgs/development/libraries/libepoxy/default.nix

@@ -13,10 +13,6 @@
 , x11Support ? !stdenv.isDarwin
 }:
 
-let
-  inherit (lib) getLib optional optionalString;
-
-in
 stdenv.mkDerivation rec {
   pname = "libepoxy";
   version = "1.5.10";
@@ -33,7 +29,7 @@ stdenv.mkDerivation rec {
   postPatch = ''
     patchShebangs src/*.py
   ''
-  + optionalString stdenv.isDarwin ''
+  + lib.optionalString stdenv.isDarwin ''
     substituteInPlace src/dispatch_common.h --replace "PLATFORM_HAS_GLX 0" "PLATFORM_HAS_GLX 1"
   '';
 
@@ -41,8 +37,9 @@ stdenv.mkDerivation rec {
 
   nativeBuildInputs = [ meson ninja pkg-config utilmacros python3 ];
 
-  buildInputs = lib.optionals x11Support [
+  buildInputs = lib.optionals (x11Support && !stdenv.isDarwin) [
     libGL
+  ] ++ lib.optionals x11Support [
     libX11
   ] ++ lib.optionals stdenv.isDarwin [
     Carbon
@@ -56,7 +53,7 @@ stdenv.mkDerivation rec {
     "-Dx11=${lib.boolToString x11Support}"
   ];
 
-  env.NIX_CFLAGS_COMPILE = lib.optionalString x11Support ''-DLIBGL_PATH="${getLib libGL}/lib"'';
+  env.NIX_CFLAGS_COMPILE = lib.optionalString (x11Support && !stdenv.isDarwin) ''-DLIBGL_PATH="${lib.getLib libGL}/lib"'';
 
   # cgl_core and cgl_epoxy_api fail in darwin sandbox and on Hydra (because it's headless?)
   preCheck = lib.optionalString stdenv.isDarwin ''