Modify some Linux flags for better GYP fidelity in GN build.

R=scottmg@chromium.org
TBR=scottmg

Review URL: https://codereview.chromium.org/134613002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244539 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244539