Apparmor cannot be built with libc++ because of GNU extension
header ext/stdio_filebuf.h. Since this header is unused,
simply drop it so that apparmor can be built with libc++.
https://bugs.launchpad.net/apparmor/+bug/1713542
https://crbug.com/759455

--- parser/libapparmor_re/aare_rules.cc
+++ parser/libapparmor_re/aare_rules.cc
@@ -23,7 +23,6 @@
 #include <iostream>
 #include <fstream>
 #include <sstream>
-#include <ext/stdio_filebuf.h>
 #include <assert.h>
 #include <stdlib.h>