Set vim's makeprg variable.

This makes :make work.

Signed-off-by: Magnus Therning <magnus@therning.org>
Ensure --appdir argument is used in `add` too.

Apparently it never was.  Oups!

Signed-off-by: Magnus Therning <magnus@therning.org>
Add a test on pkgbuild with --ghc-version.

Signed-off-by: Magnus Therning <magnus@therning.org>