configure: Try pkg-config first for libselinux

v2 (Emil) Add SELINUX_CFLAGS in the respective locations

Signed-off-by: Kusanagi Kouichi <slash@ac.auone-net.jp>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Matt Turner <mattst88@gmail.com> (v1)
4 files changed