LU-15286 build: only use baseonly option on el7

LU-15286 build: only use baseonly option on el7

el7 baseonly option allow to build perf package while
in el8 does not.

Test-Parameters: trivial

Change-Id: Ie973c5cc816b4b98ef71ab7080bd11286bcd644a
Signed-off-by: Minh Diep <mdiep@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/45677
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>