libxml2: add support for building host library with python support

Patch based on the initial work of Will Wagner (Thanks Will).
libxml2 host library with python support is required to build mesa3d (7.10.1)

Signed-off-by: Vellemans Noel <noel.vellemans@visionbms.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/libxml2/Config.in

@@ -4,3 +4,6 @@ config BR2_PACKAGE_LIBXML2
 	  XML C Parser
 
 	  http://xmlsoft.org/
+
+config BR2_PACKAGE_HOST_LIBXML2_PYTHON
+    bool

package/libxml2/libxml2.mk

@@ -26,7 +26,15 @@ LIBXML2_POST_INSTALL_STAGING_HOOKS += LIBXML2_STAGING_LIBXML2_CONFIG_FIXUP
 
 HOST_LIBXML2_DEPENDENCIES = host-pkgconf
 
-HOST_LIBXML2_CONF_OPT = --without-debug --without-python
+HOST_LIBXML2_CONF_OPT = --without-debug
+
+ifeq ($(BR2_PACKAGE_HOST_LIBXML2_PYTHON),y)
+HOST_LIBXML2_DEPENDENCIES += host-python
+HOST_LIBXML2_CONF_OPT += --with-python=$(HOST_DIR)/usr
+else
+HOST_LIBXML2_CONF_OPT += --without-python
+endif
+
 
 define LIBXML2_REMOVE_CONFIG_SCRIPTS
 	$(RM) -f $(TARGET_DIR)/usr/bin/xml2-config