MDEV-25524 fixup for Windows

In commit 54e2e701
we relaxed a debug assertion in the POSIX version of
os_file_rename_func() only. Let us relax it also on Windows,
so that the test innodb.truncate_crash will pass.

storage/innobase/os/os0file.cc

@@ -2831,7 +2831,8 @@ os_file_rename_func(
 
 	/* New path must not exist. */
 	ut_ad(os_file_status(newpath, &exists, &type));
-	ut_ad(!exists);
+	/* MDEV-25506 FIXME: Remove the strstr() */
+	ut_ad(!exists || strstr(oldpath, "/" TEMP_FILE_PREFIX_INNODB));
 
 	/* Old path must exist. */
 	ut_ad(os_file_status(oldpath, &exists, &type));