Update test-all.sh to grep for and test spvasm files.
Bug: tint:740
Change-Id: Ic43faeda35b0b1fd98e42dac2f8a515f118c5ce7
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/48690
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: David Neto <dneto@google.com>