fiddle_build_test/gyp: fix mac mesa build (2)

gyp/tools.gyp

 # Copyright 2015 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
     # GYP file to build various tools.
 #
 # To build on Linux:
 #  ./gyp_skia tools.gyp && make tools
 #
 {
@@ skipping 573 matching lines @@
             ],
             'dependencies': [
               'flags.gyp:flags',
               'skia_lib.gyp:skia_lib',
               'resources',
             ],
           },
         ],
       },
     ],
-    ['skia_os in ["linux", "mac"]',
+    ['skia_mesa and skia_os in ["linux", "mac"]',
       {
         'targets': [
           {
             'target_name': 'fiddle_build_test',
             'type': 'executable',
             'sources': [
               '../tools/fiddle/draw.cpp',
               '../tools/fiddle/fiddle_main.cpp',
               '../tools/fiddle/fiddle_main.h',
             ],
             'dependencies': [
               'skia_lib.gyp:skia_lib',
               'pdf.gyp:pdf',
             ],
             'defines': [ 'FIDDLE_BUILD_TEST' ],
-            'link_settings': { 'libraries': [ '-lOSMesa' ], },
+            'conditions': [
+              [ 'skia_os == "mac"',
+                {
+                  'link_settings': { 'libraries': [ '/opt/X11/lib/libOSMesa.dylib', ], },
+                  'include_dirs': [ '/opt/X11/include/', ],
+                }, {
+                  'link_settings': { 'libraries': [ '-lOSMesa' ], },
+                }
+              ],
+            ],
           },
         ],
       },
     ],
   ],
 }