cmd/go: report gcc ld error message when linking fails
The output of the gcc ld command is useful to understand why a package
that uses cgo can't use internal linking. We should log it.
Change-Id: Id524065fc5348be57387f2b67d1e00861f9adf15
Reviewed-on: https://go-review.googlesource.com/c/go/+/646315
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Cherry Mui <cherryyz@google.com> Reviewed-by: Ian Lance Taylor <iant@google.com>