cmd/go/internal/load: always set IsImportCycle when in a cycle
When hitting an import cycle in reusePackage, and there is already
an error set, make sure IsImportCycle is set so that we don't
end up stuck in a loop.
Fixes #25830
Change-Id: Iba966aea4a637dfc34ee22782a477209ac48c9bd
Reviewed-on: https://go-review.googlesource.com/c/go/+/301289
Trust: Roland Shoemaker <roland@golang.org>
Run-TryBot: Roland Shoemaker <roland@golang.org> Reviewed-by: Bryan C. Mills <bcmills@google.com> Reviewed-by: Jay Conrod <jayconrod@google.com>
TryBot-Result: Go Bot <gobot@golang.org>