cmd/link: add variable_parameter attr to functype outparams
When generating DW_TAG_subroutine_type DIEs during linker DWARF type
synthesis, ensure that in the list of children of the subroutine type
DIE (correspondings to input/output params) the output params are
marked with the DW_AT_variable_parameter attribute. In addition, fix
up the generated types of the output params: prior to this patch for a
given output parameter of type T, we would emit the DIE type as *T
(presumably due to how parameter passing/returning worked prior to the
register ABI); with this patch the emitted type will just be T, not *T.
Fixes #59977.
Change-Id: I5b5600be86473695663c75b85baeecad667b9245
Reviewed-on: https://go-review.googlesource.com/c/go/+/595715
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: David Chase <drchase@google.com> Reviewed-by: Cherry Mui <cherryyz@google.com>