improved third_party template to include headers as system headers for non-Windows machines
Bug: skia:
Change-Id: Id2fa74fc31b49f9b07cc83e7f60477c7ab4f8d83
Reviewed-on: https://skia-review.googlesource.com/135450
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
