Try to fix unix bustage by hard coding an include.

cmd/xfe/src/Makefile

@@ -318,6 +318,8 @@ include $(DEPTH)/config/rules.mk
 INCLUDES	+= -I$(OBJDIR) -I.. -I../DtWidgets -I$(DEPTH)/modules/libreg/include \
 		-I$(DEPTH)/dist/public/security
 
+INCLUDES	+= -I$(DEPTH)/dist/public/XfeComboBox
+
 ifdef MOZ_MAIL_NEWS
 INCLUDES	+= -I$(DEPTH)/lib/libmsg  -I$(DEPTH)/dist/public/ldap
 endif

cmd/xfe/src/Makefile.in

@@ -323,6 +323,8 @@ include $(topsrcdir)/config/rules.mk
 INCLUDES	+= -I$(OBJDIR) -I$(srcdir)/.. -I$(srcdir)/../DtWidgets -I$(topsrcdir)/modules/libreg/include \
 		-I$(DEPTH)/dist/public/security
 
+INCLUDES	+= -I$(DEPTH)/dist/public/XfeComboBox
+
 ifdef MOZ_MAIL_NEWS
 INCLUDES	+= -I$(topsrcdir)/lib/libmsg  -I$(DEPTH)/dist/public/ldap
 endif