package/{libsepol,libselinux}: fix build on ancient distros

package/{libsepol,libselinux}: fix build on ancient distros

Ancient distros (especially enterprise-grade still in use) do not accept
ln --relative.

Revert the upstream commit, since the problem it was trying to fix is
not applicable in the context of Buildroot (even with a merged /usr).

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Adam Duskett <Aduskett@gmail.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>