Allow static complication of cgo enabled libraries.

Fixes #16651

Change-Id: I0729ee4e6e5f9bd1cbdb1bc2dcbfe34463df547c
Reviewed-on: https://go-review.googlesource.com/89655
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>