Designing relocatable shebangs

Linux 7.3 brings an incredibly powerful feature: eBPF binfmt_misc hooks. You can see some discussion on this here, especially the blog post by @fzakaria here. One idea is to make the PT_INTERP elf header support $ORIGIN, so that binaries are completely relocatable. However, this breaks compatibility with older Linux kernels, and with users that otherwise cannot enable BPF. A solution is to define the normal PT_INTERP as /nix/store/..., but to additionally define a separate PT_INTERP_NIX sectio...