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)
diff --git a/configure.ac b/configure.ac
index e3a72bd..d839476 100644
--- a/configure.ac
+++ b/configure.ac
@@ -506,13 +506,15 @@
     [MESA_SELINUX="$enableval"],
     [MESA_SELINUX=no])
 if test "x$enable_selinux" = "xyes"; then
-    AC_CHECK_HEADER([selinux/selinux.h],[],
-                    [AC_MSG_ERROR([SELinux headers not found])])
-    AC_CHECK_LIB([selinux],[is_selinux_enabled],[],
-                 [AC_MSG_ERROR([SELinux library not found])])
-    SELINUX_LIBS="-lselinux"
+    PKG_CHECK_MODULES([SELINUX], [libselinux], [],
+        [AC_CHECK_HEADER([selinux/selinux.h],[],
+                         [AC_MSG_ERROR([SELinux headers not found])])
+         AC_CHECK_LIB([selinux],[is_selinux_enabled],[],
+                      [AC_MSG_ERROR([SELinux library not found])])
+         SELINUX_LIBS="-lselinux"])
     DEFINES="$DEFINES -DMESA_SELINUX"
 fi
+AC_SUBST([SELINUX_CFLAGS])
 AC_SUBST([SELINUX_LIBS])
 
 dnl Options for APIs