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: Ic075dd5a53cc76cf1b6aeca5c31db495882db915
diff --git a/.gitignore b/.gitignore
index 4a42306..2852b4d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -21,3 +21,5 @@
 *.la
 .deps
 .libs
+
+contrib/libasn1c.spec