cmd/go: don't report non-go files in CompiledGoFiles
We save non-go files in the cached srcfiles file because we want the
non-go files for vet, but we shouldn't report them in CompiledGoFiles.
Filter them out before adding them to CompiledGoFiles.
Fixes #28749
Change-Id: I889d4bbf8c4ec1348584a62ef5e4f8b3f05e97da
Reviewed-on: https://go-review.googlesource.com/c/go/+/451285
Run-TryBot: Michael Matloob <matloob@golang.org> Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Michael Matloob <matloob@golang.org>