Ninja generator: support using clang-cl for Windows 
Ninja generator: support using clang-cl for Windows 

If CC is set to 'clang-cl' in make_global_settings, use that 
as the compiler instead of cl.exe from the environment. 

BUG=chromium:82385
Review URL: https://codereview.chromium.org/136113016/

Patch from Hans Wennborg <hans@chromium.org>

old8xp/gyp_from_google,old8xp/gyp_from_google,old8xp/gyp_from_google,old8xp/gyp_from_google,old8xp/gyp_from_google