[patch, testsuite] Fix ubsan for testing when libstdc++ isn't installed

[FX]

This patch below allows ubsan to run when libstdc++ is built but not installed 
(something which happens on darwin, in particular). This fixes all 658 ubsan 
failures when run in this particular configuration.

OK to commit?
FX



2014-12-20  Francois-Xavier Coudert  <fxcoud...@gcc.gnu.org>

        * lib/ubsan-dg.exp: Add library path for libstdc++.


Index: gcc/testsuite/lib/ubsan-dg.exp
===================================================================
--- gcc/testsuite/lib/ubsan-dg.exp      (revision 218989)
+++ gcc/testsuite/lib/ubsan-dg.exp      (working copy)
@@ -47,6 +47,7 @@ proc ubsan_link_flags { paths } {
          append flags " -B${gccpath}/libsanitizer/ubsan/ "
          append flags " -L${gccpath}/libsanitizer/ubsan/.libs"
          append ld_library_path ":${gccpath}/libsanitizer/ubsan/.libs"
+         append ld_library_path ":${gccpath}/libstdc++-v3/src/.libs"
       }
     } else {
       global tool_root_dir