build: In silent rules, differentiate between .cmi and ocamlc.

Although we happen to use 'ocamlc' to compile .mli files to .cmi,
it is used in a different mode from bytecode compilation.

subdir-rules.mk

@@ -60,6 +60,9 @@ endif
 guestfs_am_v_ocamlc = $(guestfs_am_v_ocamlc_@AM_V@)
 guestfs_am_v_ocamlc_ = $(guestfs_am_v_ocamlc_@AM_DEFAULT_V@)
 guestfs_am_v_ocamlc_0 = @echo "  OCAMLC  " $@;
+guestfs_am_v_ocamlcmi= $(guestfs_am_v_ocamlcmi_@AM_V@)
+guestfs_am_v_ocamlcmi_ = $(guestfs_am_v_ocamlcmi_@AM_DEFAULT_V@)
+guestfs_am_v_ocamlcmi_0 = @echo "  OCAMLCMI" $@;
 guestfs_am_v_ocamlopt = $(guestfs_am_v_ocamlopt_@AM_V@)
 guestfs_am_v_ocamlopt_ = $(guestfs_am_v_ocamlopt_@AM_DEFAULT_V@)
 guestfs_am_v_ocamlopt_0 = @echo "  OCAMLOPT" $@;
@@ -77,7 +80,7 @@ guestfs_am_v_jar_ = $(guestfs_am_v_jar_@AM_DEFAULT_V@)
 guestfs_am_v_jar_0 = @echo "  JAR     " $@;
 
 .mli.cmi:
-	$(guestfs_am_v_ocamlc)$(OCAMLFIND) ocamlc $(OCAMLFLAGS) $(OCAMLPACKAGES) -c $< -o $@
+	$(guestfs_am_v_ocamlcmi)$(OCAMLFIND) ocamlc $(OCAMLFLAGS) $(OCAMLPACKAGES) -c $< -o $@
 .ml.cmo:
 	$(guestfs_am_v_ocamlc)$(OCAMLFIND) ocamlc $(OCAMLFLAGS) $(OCAMLPACKAGES) -c $< -o $@
 if HAVE_OCAMLOPT