build: Support make release target

Change-Id: I04b9ff47f55df0e19d8e93530fb6ccf8bdb0660b
diff --git a/Makefile.am b/Makefile.am
index 534c86e..5cffc1d 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,3 +1,5 @@
+@RELMAKE@
+
 AUTOMAKE_OPTIONS = foreign dist-bzip2 1.6
 ACLOCAL_AMFLAGS = -I m4
 
diff --git a/configure.ac b/configure.ac
index 1610973..ab63045 100644
--- a/configure.ac
+++ b/configure.ac
@@ -6,6 +6,10 @@
 dnl kernel style compile messages
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
 
+dnl include release helper
+RELMAKE='-include osmo-release.mk'
+AC_SUBST([RELMAKE])
+
 dnl checks for programs
 AC_PROG_MAKE_SET
 AC_PROG_CC