CL https://golang.org/cl/12470 has reportedly fixed the problems that
the misc/cgo/testsovar test encountered on darwin and netbsd.  Let's
actually run the test.

Update #10360.
Update #11654.

Change-Id: I4cdd27a8ec8713620e0135780a03f63cfcc538d0
Reviewed-on: https://go-review.googlesource.com/12702Reviewed-by: Russ Cox <rsc@golang.org>