All makefiles in dirs listed from mozilla/Makefile.in *must* be created by configure. The rest *should* be listed here as well.

allmakefiles.sh

@@ -523,6 +523,7 @@ widget/src/os2/Makefile
 widget/src/os2/res/Makefile
 widget/src/os2/tests/Makefile
 widget/src/qt/Makefile
+widget/src/xlibxtbin/Makefile
 widget/src/xlib/window_service/Makefile
 widget/src/xpwidgets/Makefile
 widget/src/support/Makefile