package/mesa3d: Add optional dependency xlib_libXxf86vm

xlib_libXxf86vm is an optional dependency for the DRI drivers,
quote from mesa3d/configure.ac:

    # add xf86vidmode if available
    PKG_CHECK_MODULES([XF86VIDMODE], [xxf86vm], HAVE_XF86VIDMODE=yes, HAVE_XF86VIDMODE=no)
    if test "$HAVE_XF86VIDMODE" = yes ; then
        dri_modules="$dri_modules xxf86vm"
    fi

Add the package as an optional dependency to have reproducable builds.

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/mesa3d/mesa3d.mk

@@ -82,6 +82,9 @@ MESA3D_CONF_OPT += --enable-dri3
 else
 MESA3D_CONF_OPT += --disable-dri3
 endif
+ifeq ($(BR2_PACKAGE_XLIB_LIBXXF86VM),y)
+MESA3D_DEPENDENCIES += xlib_libXxf86vm
+endif
 MESA3D_PROVIDES += libgl
 MESA3D_CONF_OPT += \
 	--enable-dri \