[asan] symbolize when possible, even if ASAN_SYMBOLIZER_PATH is not provided. On Linux this will use dl_iterate_phdr instead of /proc/self/maps, even if the symbolizer is not installed

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@182005 91177308-0d34-0410-b5e6-96231b3b80d8