Makefile.nt: remove useless rules
Makefile.nt: remove useless rules

The rules removed by this commit were cleaning the arch-specific files
and ensuring they were compiled before the dependencies were computed.

They can however be removed because there are equivalent rules in Makefile.shared.

gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml