When running libinput tools from the builddir, look up the subtools in the
builddir as well. Otherwise, add the install prefix to the list of lookup
locations.
This ensures that a) we're running builddir stuff against builddir stuff, but
also b) that we're not running builddir stuff against installed stuff because
that may give us false positives.
The test was squashed in from a separate patch and was
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
