Use release helper from libosmocore

Change-Id: Ifc88e5c942a8b430b2436d429c86560d82984a95
Related: OS#1861
diff --git a/Makefile.am b/Makefile.am
index 9e24bef..a8774c4 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -13,3 +13,5 @@
 	echo $(VERSION) > $(distdir)/.tarball-version
 
 EXTRA_DIST = .version README.md
+
+@RELMAKE@