The path to the makefile.lxc is not always static and
'/share/searx/utils/makefile.lxc' can be wrong.
When target 'lxc.activate' is called within the LXC container the path to
makefile.lxc depends on LXC_SHARE_FOLDER and the basename of the folder where
searx was cloned inital on the HOST system.
This patch determines the path of 'makefile.lxc' next to 'makefile.include'
itself.
Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>