Update libelf to FreeBSD 12 current and build as base library usable by ports
DragonFly dports graphics/mesa-dri has
FreeBSD links with its own base libelf and does not use ports devel/libelf.
FreeBSD is right in its approach. ports devel/libelf and base libelf are
different code bases. Ports or pkgsrc devel/libelf appears to have problems
with modern mesa. This can be seen using some Radeon graphics cards where
results in a completely black window when trying to start Firefox with
LD_PRELOAD=/usr/local/lib/libGL.so firefox &
What is notable about this patch is just how little the result will
differ from FreeBSD 12 current's version.