dmtcp: 2.5.2 -> 2.6.0 (#69521)

* dmtcp: 2.5.2 -> 2.6.0

Semi-automatic update generated by
https://github.com/ryantm/nixpkgs-update tools. This update was made
based on information from
https://repology.org/metapackage/dmtcp/versions

* dmtcp: disable on ARM and Darwin