external/redland: Defend against Yocto's broken xml2-config

...which is hard-coded to fail with

  echo '--should-not-have-used-/usr/bin/xml2-config'
  exit 1

Change-Id: Ic358e7d494f01f67c1469c4add080d775525ebb6

external/redland/UnpackedTarball_raptor.mk

@@ -24,6 +24,7 @@ $(eval $(call gb_UnpackedTarball_add_patches,raptor,\
 	$(if $(filter ANDROID,$(OS)),external/redland/raptor/raptor-android.patch.1) \
 	external/redland/raptor/ubsan.patch \
 	$(if $(SYSTEM_LIBXML),,external/redland/raptor/rpath.patch) \
+	external/redland/raptor/xml2-config.patch \
 ))
 
 # vim: set noet sw=4 ts=4:

external/redland/raptor/xml2-config.patch

+--- configure
++++ configure
+@@ -14197,6 +14197,11 @@
+   test -n "$XML_CONFIG" && break
+ done
+ 
++    if test -n "$XML_CONFIG"; then
++      if ! "$XML_CONFIG" --version; then
++        XML_CONFIG=
++      fi
++    fi
+   fi
+ fi
+