os: fix rmdir_all panic with hidden dirs (#9271)

vlib/os/os.v

@@ -142,8 +142,9 @@ pub fn rmdir_all(path string) ? {
 		fullpath := join_path(path, item)
 		if is_dir(fullpath) {
 			rmdir_all(fullpath) or { ret_err = err.msg }
+		} else {
+			rm(fullpath) or { ret_err = err.msg }
 		}
-		rm(fullpath) or { ret_err = err.msg }
 	}
 	rmdir(path) or { ret_err = err.msg }
 	if ret_err.len > 0 {

vlib/os/os_test.v

@@ -399,6 +399,21 @@ fn test_join() {
 	}
 }
 
+fn test_rmdir_all() {
+	mut dirs := ['some/dir', 'some/.hidden/directory']
+	$if windows {
+		for mut d in dirs {
+			d = d.replace('/', '\\')
+		}
+	}
+	for d in dirs {
+		os.mkdir_all(d) or { panic(err) }
+		assert os.is_dir(d)
+	}
+	os.rmdir_all('some') or { assert false }
+	assert !os.exists('some')
+}
+
 fn test_dir() {
 	$if windows {
 		assert os.dir('C:\\a\\b\\c') == 'C:\\a\\b'