flake/herculesCi: add aarch64-linux to ciSystems

[marijanp]

No description provided.

[marijanp]

Unfortunately the aarch64-linux build fails due to qemu reporting a segmentation fault:
https://hercules-ci.com/accounts/github/cspr-rad/derivations/%2Fnix%2Fstore%2Fiv557780lxdyrbs75aa1p0aa09ym251v-r0vm-0.21.0.drv/log?via-job=2ea40600-e62c-4c00-babb-5f5c4f4d6bdc

warning: risc0-circuit-rv32im-sys@0.21.0: qemu: uncaught target signal 11 (Segmentation fault) - core dumped
warning: risc0-circuit-rv32im-sys@0.21.0: g++: internal compiler error: Segmentation fault signal terminated program cc1plus

This is very likely associated with the fact that aarch64-linux builds are made possible by setting (boot.binfmt.emulatedSystems) to

boot.binfmt.emulatedSystems = [ "aarch64-linux" ];

in our CI agents host nixos-config.

Will need to investigate this at some point.