[llvm] r176933 - Set symbolizer path in the test environment.

[Rafael Espíndola]

> Set symbolizer path in the test environment.
>
> This is needed to get symbolized stack traces when running LLVM tests under (A|M)San.

This broke running ./bin/llvm-lit on the command line for me. Before I
could do things like

$ ./bin/llvm-lit ~/llvm/llvm/test/MC/Mips/ef_frame.ll

from the build directory, but now this turns into 'None + str', which
fails. Was this expected? How should one run a single test?

Thanks,
Rafael