cmd/link: guarantee "section .debug_gdb_scripts" is always "$GOROOT/src/runtime/runtime-gdb.py".

to guarantee the "section .debug_gdb_scripts" is  always "$GOROOT/src/runtime/runtime-gdb.py" , a check for package name is needed when search "runtime/proc.go".

Fixes #47881

Change-Id: Ib471314ca1a6777f625b488e5ae3790457540ef9
Reviewed-on: https://go-review.googlesource.com/c/go/+/344229


Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Trust: Michael Knyszek <mknyszek@google.com>