clang: Let release builds use -O3, like on gcc.

Now that http://llvm.org/bugs/show_bug.cgi?id=10031 is fixed, this will hopefully
no longer crash clang.

BUG=84815
TEST=none

Review URL: http://codereview.chromium.org/7104062

git-svn-id: http://src.chromium.org/svn/trunk/src/build@88425 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

common.gypi

@@ -641,10 +641,6 @@
           'win_release_RuntimeLibrary%': '0', # 0 = /MT (nondebug static)
           'win_debug_RuntimeLibrary%': '1',   # 1 = /MTd (debug static)
         }],
-        ['OS=="mac" and clang==1', {
-          # TODO(thakis): Remove this once http://llvm.org/PR10031 is fixed.
-          'mac_release_optimization%': '2',
-        }],
       ],
     },
     'conditions': [