The missing check was a bit buggy, and the paths were not updated
to the new 'gyp' folder instead of 'build'.

BUG=angleproject:1569

Change-Id: I10408252851e90b79e306c8aea175ebe6a931b61
Reviewed-on: https://chromium-review.googlesource.com/412320Reviewed-by: Geoff Lang <geofflang@chromium.org>