This requires widl from Wine >= 3.20:
commit b7402ddbbecdfaa81daa657fbb5d37661f401434
Author: Józef Kucia <jkucia@codeweavers.com>
Date: Mon Nov 19 15:07:02 2018 +0100
widl: Guard RPC includes with #ifdef _WIN32.
Signed-off-by: Józef Kucia <jkucia@codeweavers.com>
Signed-off-by: Henri Verbeet <hverbeet@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>