[dev.regabi] cmd/link: recognize internal/abi as runtime package

The runtime imports the internal/abi package. Recognize
internal/abi as a runtime dependent, to make trampoline generation
algorithm work.

Fix ARM build.

Change-Id: I26b6778aa41dcb959bc226ff04abe08a5a82c4f6
Reviewed-on: https://go-review.googlesource.com/c/go/+/292610


Reviewed-by: Than McIntosh <thanm@google.com>
Trust: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>