Cygwin: fsync: Fix EINVAL for block device.

The commit af8a7c13b5 has a problem that fsync returns EINVAL for
block device. This patch treats block devices as a special case.
https://cygwin.com/pipermail/cygwin/2023-January/252916.html

Fixes: af8a7c13b5 ("Cygwin: fsync: Return EINVAL for special files.")
Reported-by: Yano Ray <yanorei@hotmail.co.jp>
Reviewed-by: Corinna Vinschen <corinna@vinschen.de>
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>

winsup/cygwin/fhandler/base.cc

@@ -1728,7 +1728,8 @@ fhandler_base::utimens (const struct timespec *tvp)
 int
 fhandler_base::fsync ()
 {
-  if (!get_handle () || nohandle () || pc.isspecial ())
+  if (!get_handle () || nohandle ()
+      || (pc.isspecial () && !S_ISBLK (pc.dev.mode ())))
     {
       set_errno (EINVAL);
       return -1;

winsup/cygwin/release/3.4.6

@@ -0,0 +1,5 @@
+Bug Fixes
+---------
+
+Fix a problem that fsync returns EINVAL for block device.
+Addresses: https://cygwin.com/pipermail/cygwin/2023-January/252916.html