Enable GN build for Windows
Enable GN build for Windows

The GN build of standlone NaCl now works on Windows.
Make bots test it.

BUG= 512869
TEST= trybots

Review URL: https://codereview.chromium.org/1432043002

sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client