cmd/test: require external linking for c-archive

Change-Id: I9ceceb29291ea9f5d7b675dfabd665c5e3618471
Reviewed-on: https://go-review.googlesource.com/8955Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/dist/test.go

@@ -272,7 +272,7 @@ func (t *tester) registerTests() {
 		} else if t.hasBash() && t.goos != "android" && !iOS {
 			t.registerTest("testso", "../misc/cgo/testso", "./test.bash")
 		}
-		if t.goos == "darwin" && t.goarch == "amd64" {
+		if t.extLink() && t.goos == "darwin" && t.goarch == "amd64" {
 			// TODO(crawshaw): add darwin/arm{,64}
 			t.registerTest("testcarchive", "../misc/cgo/testcarchive", "./test.bash")
 		}