Ninja does not like having targets named 'all', and the
post-build step had some ninja-incompatible variables.

BUG=angle:529

Change-Id: Ia2bf701c997ec072b18bcbd62f7d05a2e40a1578
Reviewed-on: https://chromium-review.googlesource.com/178072Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Commit-Queue: Shannon Woods <shannonwoods@chromium.org>
Tested-by: Shannon Woods <shannonwoods@chromium.org>