These configurations were showing up in generated projects that angle is
included in because those projects don't see our common.gypi file that
marks these configurations as abstract.

Change-Id: I2c93e82567619d23f8535bd4f77446a1f837707f
Reviewed-on: https://chromium-review.googlesource.com/270282Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>