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/240553Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>