Clarify which link failed in link program perf test Bug: angleproject:8417 Change-Id: I5445518fdf6dcc2533ea055588221d6e45c45d9a Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5077412 Reviewed-by: Roman Lavrov <romanl@google.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>