targets/vdpau: Don't link unused libraries

libvdpau, libselinux and libexpat are not used.

Signed-off-by: Kusanagi Kouichi <slash@ac.auone-net.jp>
diff --git a/configure.ac b/configure.ac
index d839476..e1d4806 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1323,7 +1323,8 @@
 AM_CONDITIONAL(HAVE_ST_XVMC, test "x$enable_xvmc" = xyes)
 
 if test "x$enable_vdpau" = xyes; then
-    PKG_CHECK_MODULES([VDPAU], [vdpau >= 0.4.1 x11-xcb xcb-dri2 >= 1.8])
+    PKG_CHECK_MODULES([VDPAU], [vdpau >= 0.4.1 x11-xcb xcb-dri2 >= 1.8],
+                      [VDPAU_LIBS="`$PKG_CONFIG --libs x11-xcb xcb-dri2`"])
     GALLIUM_STATE_TRACKERS_DIRS="$GALLIUM_STATE_TRACKERS_DIRS vdpau"
 fi
 AM_CONDITIONAL(HAVE_ST_VDPAU, test "x$enable_vdpau" = xyes)