Use full name of LLVM program in error message

Previously something like `/usr/bin/opt-3.7` was being shortened to
`opt-3` using the `takeBaseName` function. This shortened form is
actually not correct. We should use `takeFileName` instead.

Reviewers: bgamari, austin, hvr

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1420

compiler/main/SysTools.hs

@@ -1329,7 +1329,7 @@ handleProc pgm phase_name proc = do
     case rc of
       ExitSuccess{} -> return r
       ExitFailure n -> throwGhcExceptionIO (
-            ProgramError ("`" ++ takeBaseName pgm ++ "'" ++
+            ProgramError ("`" ++ takeFileName pgm ++ "'" ++
                           " failed in phase `" ++ phase_name ++ "'." ++
                           " (Exit code: " ++ show n ++ ")"))
   where

testsuite/tests/driver/T8602/T8602.stderr

 A B C
-`t8602' failed in phase `Haskell pre-processor'. (Exit code: 1)
+`t8602.sh' failed in phase `Haskell pre-processor'. (Exit code: 1)