SPEC и CentOS

https://fedoraproject.org/wiki/Packaging/DistTag

A way to check for the version of Fedora in a spec file for conditional builds is:

%if 0%{?fedora} <= <version>

(The ? causes the macro to evaluate to blank if %fedora is not defined, and this causes the end result to be «0», which is a number and thus ok, while not interfering with the result if there is actually a value for %fedora.)

Я подозреваю, что

rpm --showrc|grep -i centos

выдаст что-нибудь похожее