builder: Add osinfo_config.mli file.

Every .ml file now needs a corresponding .mli file so that
dependencies are generated correctly.  The check-mli.sh script picks
up the problem:

  FAIL: check-mli.sh
  ==================
  ./builder/osinfo_config.ml: missing ./builder/osinfo_config.mli
  FAIL check-mli.sh (exit status: 1)

Fixes commit 46abca0ec3
and commit 02184f55f9.

builder/Makefile.am

@@ -54,6 +54,7 @@ SOURCES_MLI = \
 	languages.mli \
 	list_entries.mli \
 	osinfo.mli \
+	osinfo_config.mli \
 	paths.mli \
 	pxzcat.mli \
 	setlocale.mli \
@@ -359,7 +360,7 @@ CLEANFILES += \
 	console-*.out
 
 # OCaml dependencies.
-.depend: *.mli *.ml osinfo_config.ml
+.depend: *.mli *.ml osinfo_config.mli osinfo_config.ml
 	$(top_builddir)/ocaml-dep.sh $^
 -include .depend
 

builder/osinfo_config.mli

@@ -0,0 +1,21 @@
+(* virt-builder
+ * Copyright (C) 2017 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *)
+
+val libosinfo_db_path : string
+(** The path to the libosinfo database.  Note the path is generated
+    at runtime by [Makefile.am]. *)