include config.mk before we check for DOM.

lib/layout/Makefile

@@ -20,6 +20,8 @@ DEPTH		= ../..
 MODULE		= lay
 LIBRARY_NAME	= lay
 
+include $(DEPTH)/config/config.mk
+
 EXPORTS		= laylayer.h layout.h lo_funcs.h
 
 # XXX Perignon hack
@@ -71,8 +73,6 @@ ifdef DOM
 REQUIRES	+= dom
 endif
 
-include $(DEPTH)/config/config.mk
-
 ifdef MOZ_EDITOR
 CSRCS		+= layedit.c \
 		  $(NULL)