cmd/link: don't pass -gdwarf-2 to external linker

Don't pass -gdwarf-2 to the external linker when external linkage is
requested. The Go compiler is now emitting DWARF version 4, so this
doesn't seem needed any more.

Fixes #22455

Change-Id: Ic4122c55e946619a266430f2d26f06d6803dd232
Reviewed-on: https://go-review.googlesource.com/73672Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/link/internal/ld/lib.go

@@ -1073,15 +1073,15 @@ func (ctxt *Link) hostlink() {
 	argv = append(argv, *flagExtld)
 	argv = append(argv, hostlinkArchArgs(ctxt.Arch)...)
 
-	if !*FlagS && !debug_s {
-		argv = append(argv, "-gdwarf-2")
-	} else if ctxt.HeadType == objabi.Hdarwin {
+	if *FlagS || debug_s {
+		if ctxt.HeadType == objabi.Hdarwin {
 			// Recent versions of macOS print
 			//	ld: warning: option -s is obsolete and being ignored
 			// so do not pass any arguments.
 		} else {
 			argv = append(argv, "-s")
 		}
+	}
 
 	switch ctxt.HeadType {
 	case objabi.Hdarwin: