cmd/go: fix TestCgoPkgConfig on darwin with pkg-config installed
Most darwin systems don't have pkg-config installed and skip this test.
(And it doesn't run in all.bash because it is skipped during -short.)
But for those systems that have pkg-config and run the non-short tests,
it fails because the code was not writing out the bar.pc on darwin and
then expecting pkg-config to be able to tell us about the bar package.
Change the code to write out the bar entry always.
Fixes one failing case in 'go test cmd/go' on my Mac.
Change-Id: Ibc4e9826a652ce2e7c609b905b159ccf2d5a6444
Reviewed-on: https://go-review.googlesource.com/c/go/+/718182 Reviewed-by: Michael Matloob <matloob@golang.org> Reviewed-by: Michael Matloob <matloob@google.com>
Auto-Submit: Russ Cox <rsc@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>