os: fix trailing slash in dir() (#7283)

vlib/os/os.v

@@ -651,12 +651,9 @@ pub fn dir(path string) string {
 	if path == '' {
 		return '.'
 	}
-	mut pos := path.last_index(path_separator) or {
+	pos := path.last_index(path_separator) or {
 		return '.'
 	}
-	if path.ends_with(path_separator) {
-		pos--
-	}
 	return path[..pos]
 }
 

vlib/os/os_test.v

@@ -440,8 +440,10 @@ fn test_join() {
 fn test_dir() {
 	$if windows {
 		assert os.dir('C:\\a\\b\\c') == 'C:\\a\\b'
+		assert os.dir('C:\\a\\b\\') == 'C:\\a\\b'
 	} $else {
 		assert os.dir('/var/tmp/foo') == '/var/tmp'
+		assert os.dir('/var/tmp/') == '/var/tmp'
 	}
 	assert os.dir('os') == '.'
 }