cmd/compile: pointers to notinheap types need their own shape
They should not share a shape with regular pointers. We could coalesce
multiple pointer-to-not-in-heap types, but doesn't seem worth it - just
make them fully stenciled.
Fixes #51733
Change-Id: Ie8158177226fbc46a798e71c51897a82f15153df
Reviewed-on: https://go-review.googlesource.com/c/go/+/393895
Trust: Keith Randall <khr@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: David Chase <drchase@google.com>