The overlay define was placed in the libANGLE target instead of in the
config. This was causing a compile error in the capture-enabled build.

Bug: None
Change-Id: I9df02faaf57683119ca49a9b44e41ff049b05556
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2023479Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>