This test was previously disabled when external linking was
unsupported on ppc64le. It should still be disabled on ppc64
since there is no cgo or external linking there, but I removed
the if test for GOARCH=ppc64 since the initial test for cgo
enabled will cause it to be skipped on ppc64.

Fixes #22360

Change-Id: I5a0e3e4a1bd71ac7bf0ed0c792f7b78fb4a5e100
Reviewed-on: https://go-review.googlesource.com/73510
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>