test_date: Add test for quarter

This was fixed upstream in #7333, but it's a good idea to have a
test here as well, especially as we're considering switching
datetime library.

tests/by-util/test_date.rs

@@ -169,6 +169,14 @@ fn test_date_format_y() {
     scene.ucmd().arg("+%y").succeeds().stdout_matches(&re);
 }
 
+#[test]
+fn test_date_format_q() {
+    let scene = TestScenario::new(util_name!());
+
+    let re = Regex::new(r"^[1-4]\n$").unwrap();
+    scene.ucmd().arg("+%q").succeeds().stdout_matches(&re);
+}
+
 #[test]
 fn test_date_format_m() {
     let scene = TestScenario::new(util_name!());