test(runtime/syntax): improve syntax tests

When a syntax file is changed, timestamps of the corresponding files are
updated.

NOTE: At the moment this script does not strictly track dependency, like
cpp on c.

Also update ignore files

closes #16548

Co-authored-by: Aliaksei Budavei <0x000c70@gmail.com>
Signed-off-by: Eisuke Kawashima <e-kwsm@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/syntax/testdir/README.txt b/runtime/syntax/testdir/README.txt
index 6703228..d8ac066 100644
--- a/runtime/syntax/testdir/README.txt
+++ b/runtime/syntax/testdir/README.txt
@@ -67,8 +67,8 @@
 
 	make test
 
-Or you can run the tests for a filetype only by passing its file extension as
-another target, e.g. "java", before "test":
+Or you can run the tests for a filetype only by passing its name as another
+target, e.g. "java", before "test":
 
 	make java test