test/Driver/cpath.c: Escape a few args that contain %{pathsep}.

On msys bash, with %pathsep==os.pathsep==';', I can see lines like below in this script;

    env DIR=X:/foo%{pathsep}X:/bar

Then it is expanded to;

    env DIR=X:/foo;X:/bar

It should be with quote;

    env "DIR=X:/foo;X:/bar"

llvm-svn: 153402