Link .mli files corresponding to autorgenerated .ml files into builddir

Link .mli files corresponding to autorgenerated .ml files into builddir

This avoids build failures in separate builds such as this one:

,----
| ocamlfind ocamlc -package str,unix -I . -a guestfs_config.cmo stringMap.cmo stringSet.cmo std_utils.cmo -o mlstdutils.cma
| ar cr libmlstdutils.a libmlstdutils_a-dummy.o
| ranlib libmlstdutils.a
| File "_none_", line 1:
| Error: Files std_utils.cmo and guestfs_config.cmo
|        make inconsistent assumptions over interface Guestfs_config
| make[4]: *** [Makefile:2580: mlstdutils.cma] Error 2
`----

Gbp-Pq: Name 0018-Link-.mli-files-corresponding-to-autorgenerated-.ml-.patch