I also use make -j for C++ with great success. And so I am also stuck with having to declare my functions in a separate file from where they're defined, and thus when stepping through code with a debugger or just a good source viewer that can jump to callers/callees, I never see the comments because they're in the header not the source. Not to mention the problems I run into when linking with a library that was compiled with different options or a different version of the source. And bending over backwards to implement concurrent algorithms to get decent runtime performance, and debugging the inevitable bugs that follow.
Rust focuses on a different set of optimizations. I'm still working out when I prefer the Rust set or the C++ set or the Python set. I want to love Rust, but when doing exploratory work with unfamiliar APIs, the slow recompile loop and need to get everything correct for each incremental experimental build I do to try to figure out how something works is pretty painful. I don't know how much better it gets with familiarity. Rust is very nice when I fully understand the problem I'm solving and the environment I'm working in, and I vastly prefer it to C++ for that. But I frequently dive into unfamiliar codebases to make modifications.