configure.ac: require xcb* for the omx/va/... when using x11 platform

Targets such as omx and va can work w/o anything X related. Mandate the
xcb* dependencies only when the X11 platform is selected.

Reported-by: Lukas Rusak <lorusak@gmail.com>
Fixes: 63e11ac2b5c ("configure: error out if building VA w/o supported
platform")
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
Tested-by: Lukas Rusak <lorusak@gmail.com> (v1)
diff --git a/configure.ac b/configure.ac
index dafc9f8..59a111a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2156,7 +2156,9 @@
         "x$enable_vdpau" = xyes -o \
         "x$enable_omx_bellagio" = xyes -o \
         "x$enable_va" = xyes; then
-    PKG_CHECK_MODULES([VL], [x11-xcb xcb xcb-dri2 >= $XCBDRI2_REQUIRED])
+    if echo $platforms | grep -q "x11"; then
+        PKG_CHECK_MODULES([VL], [x11-xcb xcb xcb-dri2 >= $XCBDRI2_REQUIRED])
+    fi
     need_gallium_vl_winsys=yes
 fi
 AM_CONDITIONAL(NEED_GALLIUM_VL_WINSYS, test "x$need_gallium_vl_winsys" = xyes)