mac: Use -O2 for clang release builds for now.

BUG=none
TEST=none


Review URL: http://codereview.chromium.org/7083014

git-svn-id: http://src.chromium.org/svn/trunk/src/build@87141 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

common.gypi

@@ -634,6 +634,10 @@
       ],
     },
     'conditions': [
+      ['OS=="mac" and clang==1', {
+        # TODO(thakis): Remove this once http://llvm.org/PR10031 is fixed.
+        'mac_release_optimization%': '2',
+      }],
       ['branding=="Chrome"', {
         'defines': ['GOOGLE_CHROME_BUILD'],
       }, {  # else: branding!="Chrome"