build-sys: autodetect and use pkg-config for libselinux

Hi!
libselinux has a pkg-config file:

$ rpm -qf /usr/lib64/pkgconfig/libselinux.pc
libselinux-devel-2.0.98-alt1

$ cat /usr/lib64/pkgconfig/libselinux.pc
prefix=/usr
exec_prefix=${prefix}
libdir=${exec_prefix}/lib64
includedir=/usr/include

Name: libselinux
Description: SELinux utility library
Version: 2.0.98
URL: http://userspace.selinuxproject.org/
Libs.private: -lsepol
Libs: -lselinux
Cflags:

Patch for use pkg-config in attach.

--
Alexey Shabalin

configure.ac

@@ -115,21 +115,15 @@ PKG_CHECK_MODULES(DBUS, [ dbus-1 >= 1.3.2 ])
 AC_SUBST(DBUS_CFLAGS)
 AC_SUBST(DBUS_LIBS)
 
-have_selinux=no
-AC_ARG_ENABLE(selinux, AS_HELP_STRING([--disable-selinux], [Disable optional SELINUX support]))
-if test "x$enable_selinux" != "xno"; then
-	# not using PKG_CHECK_MODULES as for some reason libselinux didn't
-	# install any pkg-config modules here
-	AC_SEARCH_LIBS([getcon], [selinux],
-                [AC_DEFINE(HAVE_SELINUX, 1, [Define if SELINUX is available]) have_selinux=yes],
-		have_selinux=no)
-        AC_SUBST(SELINUX_CFLAGS)
-        AC_SUBST(SELINUX_LIBS)
-        if test "x$have_selinux" = xno -a "x$enable_selinux" = xyes; then
-                AC_MSG_ERROR([*** selinux support requested but libraries not found])
-        fi
+PKG_CHECK_MODULES(SELINUX, libselinux,
+	have_selinux=yes,
+	have_selinux=no)
+if test "x$have_selinux" = "xyes" ; then
+	AC_DEFINE(HAVE_SELINUX, [], [Define if SELINUX is available])
 fi
-AM_CONDITIONAL(HAVE_SELINUX, [test "$have_selinux" = "yes"])
+AM_CONDITIONAL(HAVE_SELINUX, test x$have_selinux = xyes)
+AC_SUBST(SELINUX_CFLAGS)
+AC_SUBST(SELINUX_LIBS)
 
 AC_ARG_ENABLE([tcpwrap],
         AS_HELP_STRING([--disable-tcpwrap],[Disable optional TCP wrappers support]),