[dev.link] cmd/link: add a test for trampoline insertion
[dev.link] cmd/link: add a test for trampoline insertion

Now that we have converted pclntab pass to using the loader,
trampoline insertion should work again. Add a test.

Change-Id: Ia9a0485456ac75cc6e706218a359f109cd8fce43
Reviewed-on: https://go-review.googlesource.com/c/go/+/228141
Reviewed-by: Than McIntosh <4b2922593166fc595a9b1a408f34f5d3817fe9d2@google.com>

golang/go,akutz/go,cloudflare/go,golang/go,akutz/go,CAFxX/go,nawawi/go,CAFxX/go,golang/go,nawawi/go,nawawi/go,akutz/go,CAFxX/go,cloudflare/go,akutz/go,CAFxX/go,golang/go,akutz/go,golang/go,cloudflare/go,akutz/go,cloudflare/go,akutz/go,CAFxX/go,cloudflare/go,nawawi/go,CAFxX/go,akutz/go,CAFxX/go,golang/go,cloudflare/go,CAFxX/go,golang/go,cloudflare/go,nawawi/go,cloudflare/go,golang/go,nawawi/go,nawawi/go,nawawi/go