cmd/link: recognize clang linker error in testCGOLTO
Also recognize a case in which GCC does not run (from
https://build.golang.org/log/
7f6d8b35c905b9829f05906beccca44f208aa569).
Fixes #46517
Change-Id: I4fe4164a5df92b2dec08fd767f65a4d5479f3f36
Reviewed-on: https://go-review.googlesource.com/c/go/+/324169
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>