Cmake fish build performance improvement needed

[Matthew-Benson]

Fish's slow Cmake toolchain is causing slow development cycles. Currently it takes me on average roughly 2 minutes for Fish to compile on my desktop. Not sure if cmake cache options can speed things up here? The user experience is not great when you're waiting for long build times, and supporting a binary artifact vs compiling from source may only be available in Fish 3.8+ with their Rust rewrite (will create a follow-up issue for this).

This needs further investigation.