htop does not really need cgroups enabled in kernel for a runtime. I have this feature completely disabled and having zero troubles regarding this. CONFIG_CHECK in ebuild would need a change and move into pkg_postinst message. Maybe it needs cgroups to provide information about cgroups but it's not for htop itself.
* Messages for package sys-process/htop-2.0.0-r1:
* To use lsof features in htop(what processes are accessing
* what files), you must have sys-process/lsof installed.
* CONFIG_CGROUPS: is not set when it should be.
* Please check to make sure these options are set correctly.
* Failure to do so may cause unexpected problems.
If the linux kernel doesn't support cgroups (CONFIG_CGROUPS is not enabled), this ebuild will emit the warning message "CONFIG_CGROUPS: is not set when it should be."
However, the htop build (provided by upstream) will proceed without any errors. Its configure script is passed the "--enable-cgroup" option and does not complain.
The htop executable does not use cgroups functionality, other than to show a process's cgroup. By default, this column is not included in the output. If this column is added to the output, but the kernel does not support cgroups, then htop displays "(null)".
A couple possible solutions:
1. Add a "cgroup" use flag to the ebuild
2. Remove "~CGROUPS" from CONFIG_CHECK