Support RPM building via contrib/osmo-e1-recorder.spec.in

Change-Id: I1851b5c2a68ec9559e42c9da3f04d43c0fc7cdfe
diff --git a/configure.ac b/configure.ac
index 65a2c7f..568584d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -192,4 +192,5 @@
     doc/Makefile
     tests/Makefile
     doc/examples/Makefile
+    contrib/osmo-e1-recorder.spec
     Makefile)