contrib: integrate RPM spec

Remove OpenSUSE bug report link, set version to @VERSION@, make it build
with CentOS 8 etc.

Related: OS#4550
Change-Id: Iba04d5c7b9beee80baca83063f9cb2cd533a0003
diff --git a/.gitignore b/.gitignore
index 7dec8a9..cb27dff 100644
--- a/.gitignore
+++ b/.gitignore
@@ -79,3 +79,5 @@
 doc/manuals/osmomsc-usermanual.xml
 doc/manuals/common
 doc/manuals/build
+
+contrib/osmo-ggsn.spec