Useful for debugging when an uninitialized id is used in the SPIR-V
transformer.

Bug: angleproject:4888
Change-Id: If446187a8a27a06f5958d5df5bc00d02e98d20e3
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2713268
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>