Don't crash if find_executable return None.

This was crashing when trying to run the tests on Windows.

llvm-svn: 220048

llvm/test/Bindings/Go/lit.local.cfg

@@ -36,14 +36,14 @@ def fixup_compiler_path(compiler):
     try:
         if path.endswith('/cc') and os.readlink(path) == 'clang':
             args[0] = path[:len(path)-2] + 'clang'
-    except OSError:
-        skip
+    except AttributeError:
+        pass
 
     try:
         if path.endswith('/c++') and os.readlink(path) == 'clang++':
             args[0] = path[:len(path)-3] + 'clang++'
-    except OSError:
-        skip
+    except AttributeError:
+        pass
 
     return ' '.join([pipes.quote(arg) for arg in args])