Fix Linux build, and update BUILD.gn. Re-re-land with fixes for Linux and Android. We were getting multiply defined symbol errors on Linux for some stuff in the common sources. Switch to using a static lib target for the common sources, and also sync BUILD.gn with the latest gyp. BUG=angle:773 Change-Id: Ia2d52978a167c532e5e76cb711de589855eff44e Reviewed-on: https://chromium-review.googlesource.com/240553 Tested-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>