Don't use -fno-ident for Clang builds in Release mode on Linux.
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: de016e52bd170d2d4f2344f9bf92d50478b649e0@62381 0039d316-1c4b-4281-b951-d872f2087c98

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