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: I59255889740195ec811a947a7130ae0918ea4b4d
diff --git a/.gitignore b/.gitignore
index 5224233..a9dd303 100644
--- a/.gitignore
+++ b/.gitignore
@@ -99,3 +99,5 @@
 # code coverage reports
 libosmocore-*-coverage*
 coverage-cobertura.xml
+
+contrib/libosmocore.spec