Bug 298431 - Rewrite xforms build system so it works with XULRunner

This is an additional patch which fixes the 'distclean' target for AIX.
p=allan@beaufour.dk, r=benjamin@smedbergs.us

extensions/xforms/Makefile.in

@@ -184,7 +184,7 @@ CPPSRCS		= \
 EXTRA_DSO_LDOPTS = $(MOZ_COMPONENT_LIBS)
 
 # Do not clean schema-validation on distclean, it should handle that itself
-distclean:: DIRS=
+distclean:: LOOP_OVER_DIRS=
 
 include $(topsrcdir)/config/rules.mk