Makefile.am: EXTRA_DIST: debian, contrib/*.spec.in

Change-Id: I13f28041adcc1530e5125775c4533d8ac0a88169
diff --git a/Makefile.am b/Makefile.am
index d08f41b..f2a05a9 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -28,7 +28,15 @@
 dist-hook:
 	echo $(VERSION) > $(distdir)/.tarball-version
 
-EXTRA_DIST = git-version-gen .version README.md osmo-release.mk osmo-release.sh
+EXTRA_DIST = \
+	     .version \
+	     README.md \
+	     contrib/libosmocore.spec.in \
+	     debian \
+	     git-version-gen \
+	     osmo-release.mk \
+	     osmo-release.sh \
+	     $(NULL)
 
 HTML = \
 	$(top_builddir)/doc/core/html/index.html \