Minor fixes for ASan/TSan bots:
 - fix PATH to include GCC 4.8
 - do not run the tests if compilation fails
 - set LD_LIBRARY_PATH


git-svn-id: http://address-sanitizer.googlecode.com/svn/trunk@2100 3c3640eb-14a6-2bb8-0b94-e9e73afe33f5