75% is really good even if it requires changing the toolchain. Have you tried https://github.com/firebuild/firebuild ? It is a caching accelerator and it can cache the linking and the buildscripts, too in Rust builds. It can make your builds more than 90% faster, especially with low cores counts. https://balintreczey.hu/blog/improve-build-time-of-rust-java... The Mac port is experimental, though.