Do not try to set restorecon_last on /sys entries.

There is no benefit to setting restorecon_last on /sys entries
since they are re-created on each boot and doing so triggers
sys_admin denials.   Also, apply the same partial matching
optimization to restorecon_recursive on subdirectories of /sys
as we apply on the top-level restorecon_recursive /sys.

Change-Id: I90ea143e189db44bf8dc6c93c08d794e80d5539f
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Add basic Makefile.

With this Makefile libselinux.a and libselinux.so can be built without
the entire Android build system.

Signed-off-by: Markus Mayer <code@mmayer.net>