cmd/cgo/internal/testcarchive: fix nocgo and no-c-archive builds
CL 495918 enabled testcarchive much more widely and added many dynamic
test skips. CL 495855 added TestDeepStack before these dynamic skips
were in. Unfortunately, the two CLs don't logically commute, so when
CL 495918 landed, it broke at least nocgo builders and platforms that
don't support c-archive builds. Fix this by adding the necessary skips
to TestDeepStack.