fiddle_build_test depends on skia_mesa

Builds on Build-Ubuntu-GCC-x86_64-Release-Mesa-Trybot

Shouldn't break anything else.

Review URL: https://codereview.chromium.org/1901823002
diff --git a/gyp/tools.gyp b/gyp/tools.gyp
index 0f94350..9c5cfab 100644
--- a/gyp/tools.gyp
+++ b/gyp/tools.gyp
@@ -34,7 +34,9 @@
         'whitelist_typefaces',
       ],
       'conditions': [
-        # ['skia_os == "linux"', { 'dependencies': [ 'fiddle_build_test' ] } ],
+        ['skia_mesa and skia_os in ["linux", "mac"]',
+          { 'dependencies': [ 'fiddle_build_test' ] }
+        ],
         ['skia_shared_lib',
           {
             'dependencies': [