cmd/link/internal/ld: ensure mach-o debug symbols are visible to App Store

Passing test that shows Apple's symbols utility can now read
DWARF data in go.o, after the fix in CL174538

Updates #31022 #22716 #31459

Change-Id: I56c3517ad6d0a9f39537182f63cef56bb198aa83
Reviewed-on: https://go-review.googlesource.com/c/go/+/170451Reviewed-by: Than McIntosh <thanm@google.com>

src/cmd/link/dwarf_test.go

@@ -98,6 +98,8 @@ func testDWARF(t *testing.T, buildmode string, expectDWARF bool, env ...string)
 						if bytes.HasPrefix(out, []byte("Unable to find file")) {
 							// This failure will cause the App Store to reject our binaries.
 							t.Fatalf("symbols %v: failed to parse file", filepath.Base(exe))
+						} else if bytes.Contains(out, []byte(", Empty]")) {
+							t.Fatalf("symbols %v: parsed as empty", filepath.Base(exe))
 						}
 					}
 				}