gyp: Fix missing ENABLE defs in end2end_tests. These defines are necessary for config filtering. BUG=angleproject:1660 Change-Id: I5bc32d8127023a0de32af75101eda13c5cdf849e Reviewed-on: https://chromium-review.googlesource.com/425090 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>