Use release helper from libosmocore

Change-Id: I06b9ceff1e1ecfccc1b1a52ffe6b9d3f6dcaa34d
Related: OS#1861
diff --git a/Makefile.am b/Makefile.am
index 0d60cee..392d80d 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -10,6 +10,8 @@
 	.version \
 	$(NULL)
 
+@RELMAKE@
+
 BUILT_SOURCES = $(top_srcdir)/.version
 $(top_srcdir)/.version:
 	echo $(VERSION) > $@-t && mv $@-t $@