Only remove buildconfig.html when you 'make distclean'. Otherwise doing 'make clean' in toolkit means that you need to re-run configure.

toolkit/Makefile.in

@@ -52,13 +52,16 @@ CHROME_DEPS	= locale/build.dtd content/buildconfig.html
 
 include $(topsrcdir)/config/rules.mk
 
-GARBAGE	+= content/buildconfig.html locale/build.dtd
+GARBAGE	+= locale/build.dtd
 
 locale/build.dtd: locale/build.dtd.in $(DEPTH)/config/build_number
 	@$(RM) -f $@
 	@if test ! -d locale; then mkdir locale; fi
 	$(PERL) -I$(topsrcdir)/config $(topsrcdir)/config/aboutime.pl $@ $(DEPTH)/config/build_number $(srcdir)/locale/build.dtd.in
 
+distclean::
+	$(RM) -f content/buildconfig.html
+
 # skin/unix contains css rules that more closely match gtk widgets
 ### killing this for now until we know how qute looks on linux
 # ifneq (,$(filter gtk gtk2,$(MOZ_WIDGET_TOOLKIT)))