cmd/link,runtime: DWARF/gdb support for swiss maps

cmd/link,runtime: DWARF/gdb support for swiss maps

For #54766.

Cq-Include-Trybots: luci.golang.try:gotip-linux-ppc64_power10,gotip-linux-amd64-longtest-swissmap
Change-Id: I6695c0b143560d974b710e1d78e7a7d09278f7cc
Reviewed-on: https://go-review.googlesource.com/c/go/+/620215
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>