[PATCH, ubsan, obvious] Fix typo in string empty check

[Kirill Yukhin]

Hello,
Patch in the bottom fixes typo in check of for string emptiness
gcc/
    * gcc/ubsan.c (ubsan_use_new_style_p): Fix check for empty string.

I'll bootstrap/regtest the patch and check it into as obvious if no 
objections.

--
Thanks, K

commit 57ad19906b808386220d628a1ba326e043e0d211
Author: Kirill Yukhin <kirill.yuk...@gmail.com>
Date:   Fri Sep 2 23:14:05 2016 +0300

    Compare first element of char* instead of pointer.

diff --git a/gcc/ubsan.c b/gcc/ubsan.c
index 5cbc98d..d3bd8e3 100644
--- a/gcc/ubsan.c
+++ b/gcc/ubsan.c
@@ -1469,7 +1469,7 @@ ubsan_use_new_style_p (location_t loc)

   expanded_location xloc = expand_location (loc);
   if (xloc.file == NULL || strncmp (xloc.file, "\1", 2) == 0
-      || xloc.file == '\0' || xloc.file[0] == '\xff'
+      || xloc.file[0] == '\0' || xloc.file[0] == '\xff'
       || xloc.file[1] == '\xff')
     return false;