Cygwin: rmdir: handle /dev in fhandler_dev::rmdir

The isdev_dev check in rmdir is unclean.  Create a virtual method
fhandler_dev::rmdir to handle this transparently.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/dir.cc

@@ -410,8 +410,6 @@ rmdir (const char *dir)
 	set_errno (ENOENT);
       else if (has_dot_last_component (dir, false))
 	set_errno (EINVAL);
-      else if (isdev_dev (fh->dev ()))
-	set_errno (ENOTEMPTY);
       else if (!fh->rmdir ())
 	res = 0;
       delete fh;

winsup/cygwin/fhandler.h

@@ -1765,6 +1765,7 @@ public:
   int close ();
   int __reg2 fstat (struct stat *buf);
   int __reg2 fstatvfs (struct statvfs *buf);
+  int rmdir ();
   DIR __reg2 *opendir (int fd);
   int __reg3 readdir (DIR *, dirent *);
   void rewinddir (DIR *);

winsup/cygwin/fhandler_dev.cc

@@ -107,6 +107,13 @@ fhandler_dev::fstatvfs (struct statvfs *sfs)
   return ret;
 }
 
+int
+fhandler_dev::rmdir ()
+{
+  set_errno (ENOTEMPTY);
+  return -1;
+}
+
 DIR *
 fhandler_dev::opendir (int fd)
 {