buildroot

xapp_xload: fix musl build

xapp_xload tries to include protocols/rwhod.h, which isn't available on
musl. Fortunately, the package also has stub code that can be enabled
with -DRLOADSTUB (this is done e.g. on Cygwin).

This should probably be detected in configure, but that's a lot more
work.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>