Fixes to prep_libc.py to support correct stripping of x64 libcmt on x64 target

BUG=166496

Review URL: https://chromiumcodereview.appspot.com/12258025

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@182457 0039d316-1c4b-4281-b951-d872f2087c98
1 file changed