This enables tools again which has been disabled in commit
498506af9 ("libupnp: update to 1.14.5"). Disabling tools leads to the
header upnptools.h not being installed into /usr/include. But e.g. mpd-full
depends on this header.
Fixes: 498506af9 ("libupnp: update to 1.14.5")
Signed-off-by: Alexander Egorenkov <egorenar-dev@posteo.net>