cmd/link/internal/ld: don't link with -no_pie on darwin/arm64

Ever since CL 33301 linking darwin/arm64 excutables has resulted in
warnings like:

ld: warning: -no_pie ignored for arm64

Remove -no_pie on darwin/arm64.

Change-Id: I9f7685351fa8cce29795283e1a24fc7a6753d698
Reviewed-on: https://go-review.googlesource.com/42815
Run-TryBot: Elias Naur <elias.naur@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

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

@@ -1050,7 +1050,7 @@ func (l *Link) hostlink() {
 		argv = append(argv, "-Wl,-headerpad,1144")
 		if l.DynlinkingGo() {
 			argv = append(argv, "-Wl,-flat_namespace")
-		} else {
+		} else if !SysArch.InFamily(sys.ARM64) {
 			argv = append(argv, "-Wl,-no_pie")
 		}
 	case objabi.Hopenbsd: