misc/cgo/testcarchive: skip TestExtar on self-hosted iOS

iOS cannot (directly) run shell scripts.

Updates #31722

Change-Id: I69473e9339c50a77338d391c73b4e146bce3fa89
Reviewed-on: https://go-review.googlesource.com/c/go/+/174700
Run-TryBot: Elias Naur <mail@eliasnaur.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

misc/cgo/testcarchive/carchive_test.go

@@ -525,6 +525,9 @@ func TestExtar(t *testing.T) {
 	if runtime.Compiler == "gccgo" {
 		t.Skip("skipping -extar test when using gccgo")
 	}
+	if runtime.GOOS == "darwin" && (runtime.GOARCH == "arm" || runtime.GOARCH == "arm64") {
+		t.Skip("shell scripts are not executable on iOS hosts")
+	}
 
 	defer func() {
 		os.Remove("libgo4.a")