Install mozilla-config.h into SDK dir.

Bug 170377 r=dougt

config/Makefile.in

@@ -106,6 +106,8 @@ export:: $(TARGETS) $(HEADERS)
 	-rm -f $(FINAL_LINK_COMPS) $(FINAL_LINK_LIBS) $(FINAL_LINK_COMP_NAMES)
 	-rm -f $(DIST)/bin/chrome/chromelist.txt
 
+export:: $(DEPTH)/mozilla-config.h
+	$(NSINSTALL) -t -m 444 $< $(DIST)/sdk/
 
 # Create mini-SDK directory for NSPR
 ifndef MOZ_NATIVE_NSPR