LU-18613 lbuild: fix RPMBUILD in lbuild

LU-18613 lbuild: fix RPMBUILD in lbuild

lbuild should return an error when rpmbuild is not found
in check_options(). The check for rpm is not needed because
it's not used for building RPM package.

Test-Parameters: trivial

Change-Id: I6572110c6362a941f130d65d6734bdebbc6acc82
Signed-off-by: Jian Yu <yujian@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/57662
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>