clang: Set clang-specific flags on linux only if the target compiler is used.
clang: Set clang-specific flags on linux only if the target compiler is used.

The host compiler is hardcoded to gcc in the linux make build, and gcc does
not understand all of these options.

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/6487005

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@74479 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser