When trying to do bisection debugging, the pnacl-llc translation was happening every time even if the pexe didn't change.  This is because it was checking for a binary called 'llc' in the current directory, instead of an absolute path the pnacl-llc.  (This check is done so that updating pnacl-llc triggers a rebuild of the bisection binary, similar to the check for an update of pnacl-sz.)

BUG= none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/1044623003