MDEV-29522 RocksDB RPM doesn't get built on Rocky Linux and Alma

use correct python on rocky8 and alma8

cmake/cpack_rpm.cmake

@@ -283,7 +283,7 @@ ELSEIF(RPM MATCHES "sles")
     "mariadb-server = %{version}-%{release}"
   )
 ENDIF()
-IF(RPM MATCHES "fedora31" OR RPM MATCHES "(rhel|centos)8")
+IF(RPM MATCHES "fedora31" OR RPM MATCHES "(rocky|alma|rhel|centos)8")
   SET(PYTHON_SHEBANG "/usr/bin/python3" CACHE STRING "python shebang")
 ENDIF()