t030[02]: work around CR/LF issue

It is the old shell-script issue we had in a few other tests already.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

t/lib-credential.sh

@@ -19,6 +19,10 @@ check() {
 		false
 	fi &&
 	test_cmp expect-stdout stdout &&
+	if test_have_prereq MINGW
+	then
+		dos2unix stderr
+	fi &&
 	test_cmp expect-stderr stderr
 }