makedep: Output empty rule for source makefiles.

This should avoid breaking the build when a makefile is removed.

Signed-off-by: Alexandre Julliard <julliard@winehq.org>

tools/makedep.c

@@ -3151,6 +3151,8 @@ static struct strarray output_sources( const struct makefile *make )
         output( "Makefile:" );
         output_filenames( makefile_deps );
         output( "\n" );
+        output_filenames( makefile_deps );
+        output( ":\n" );
         output( "distclean::\n");
         output( "\trm -f" );
         output_filenames( distclean_files );