The first thing you see when trying to bootstrap is that it tries to use exceptions.
I'm not sure how this wasn't an issue when I initially ported it, but it's a problem now 🤷
Not sure why, but adding -fexceptions to CXXFLAGS does not make the compiler accept the throws, and there are quite a few of them used across CMake's codebase.

We could probably patch them out, since the ones I saw were caught only to signal an error, and crashing instead should be just fine (if a little sad).
Alternatively we could go the way of adding exception support one way or another, but enable them only for the ports that need it.