Don't use -fno-ident for Clang builds in Release mode on Linux.

It's not supported by Clang and causes a ton of "argument unused
during compilation" warnings.

BUG=none
TEST=everything still builds

Review URL: http://codereview.chromium.org/3614013

git-svn-id: http://src.chromium.org/svn/trunk/src/build@62381 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

common.gypi

@@ -991,6 +991,11 @@
                   '-Wl,--gc-sections',
                 ],
               }],
+              ['clang==1', {
+                'cflags!': [
+                  '-fno-ident',
+                ],
+              }],
             ]
           },
         },