I believe this will break the bootstrap version of cat that is needed for building on Linux/macOS since caph_enter_casper() will fail there.
This probably needs a few more #ifndef BOOTSTRAP_CAT.
If you have a github fork, the github actions will test the non-FreeBSD build automatically for the "main" branch of your repository.
Otherwise this seems fine to me.
I just needed to add a new service to the tools/build/Makefile and it work like charm - https://github.com/oshogbo/freebsd-src/runs/1710760934 (mac will finish in a moment).
Do you want me to test something else?
So in the case of the building rescue and the bootstrapping, we are using the libcapsicum/Casper headers that replace the caph_* functions with empty ones.