neon: explicit path to xml2-config

Now that $(STAGING_DIR)/usr/bin is not in the PATH, we need to
explicit the path to such tools.

This might also fix bug 1393 since by expliciting the path to
xml2-config, we'll force neon ./configure to choose our xml2-config
and not the one of the host.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/neon/neon.mk

@@ -14,6 +14,7 @@ NEON_DEPENDENCIES:=host-pkg-config
 ifeq ($(BR2_PACKAGE_NEON_LIBXML2),y)
 NEON_CONF_OPT+=--with-libxml2=yes
 NEON_CONF_OPT+=--with-expat=no
+NEON_CONF_ENV+=ac_cv_prog_XML2_CONFIG=$(STAGING_DIR)/usr/bin/xml2-config
 NEON_DEPENDENCIES+=libxml2
 endif
 ifeq ($(BR2_PACKAGE_NEON_ZLIB),y)