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: I3e135e5e7807688366598a24e121550d6292906c
diff --git a/.gitignore b/.gitignore
index 08b34f1..2eee9cd 100644
--- a/.gitignore
+++ b/.gitignore
@@ -44,3 +44,5 @@
 
 # vi/vim files
 *.sw?
+
+contrib/libosmo-abis.spec