I've installed frama-c using opam (on Ubuntu 16.04). 
I try to install the "hello\_world.ml" as plugin (of the plugin development guide) using a Makefile

```
    FRAMAC_SHARE :=$(shell frama-c.byte -print-path)
    FRAMAC_LIBDIR :=$(shell frama-c.byte -print-libpath)
    PLUGIN_NAME = Hello
    PLUGIN_CMO = hello_word
    include $(FRAMAC_SHARE)/Makefile.dynamic

```

Running make, I get this:

```
     /home/amira/.opam/system/share/frama-c/Makefile.dynamic:295: .depend: Aucun fichier ou dossier de ce type
     /home/amira/.opam/system/share/frama-c/Makefile.plugin:204: *** "The file 'Hello.mli' must be provided. The simplest workaround is 'touch Hello.mli'.". Arrêt.

```

How can I resolve this error?