As per the discussion in
https://salsa.debian.org/kernel-team/linux/-/merge_requests/1005 - once vmlinux.h is included with linux-headers, the warning about cmd_btf_ko etc. should be harmless, as that file should already be available (ie: there's no need to generate it again as part of kernel build). Am I missing something else? I confess I have only a very small amount of experience with BPF code; I played with building a few modules, but I don't use it regularly.