x264: disable avxsynth support

Fixes:
http://autobuild.buildroot.net/results/0f8/0f8b1167ba23a9a2cd9bd6b6e1baa0470523d47d/
http://autobuild.buildroot.net/results/b65/b651f488fbd6f2985e1a656814098db6c60040e5/

We don't have an avxsynth package in Buildroot, and x264 uses dlopen to
access it so it breaks on static only toolchains.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/x264/x264.mk

@@ -11,6 +11,7 @@ X264_LICENSE = GPLv2+
 X264_DEPENDENCIES = host-pkgconf
 X264_LICENSE_FILES = COPYING
 X264_INSTALL_STAGING = YES
+X264_CONF_OPTS = --disable-avs
 
 ifeq ($(BR2_i386)$(BR2_x86_64),y)
 X264_DEPENDENCIES += host-yasm