vendor.conf: add ostree-go

it is used by containers/image for pulling images to the OSTree storage.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

vendor/github.com/ostreedev/ostree-go/pkg/glibobject/glibobject.go.h

@@ -0,0 +1,17 @@
+#include <glib.h>
+
+static char *
+_g_error_get_message (GError *error)
+{
+  g_assert (error != NULL);
+  return error->message;
+}
+
+static const char *
+_g_variant_lookup_string (GVariant *v, const char *key)
+{
+  const char *r;
+  if (g_variant_lookup (v, key, "&s", &r))
+    return r;
+  return NULL;
+}