The parent makefile will recursively call all submakefiles for various
targets among which install. So this makefile needs to handle that even
if it doesn't do anything

Signed-off-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
Reviewed-by: Guillaume Desmottes <guillaume.desmottes@collabora.co.uk>
Differential Revision: https://phabricator.apertis.org/D5249