Another Nim user here. Typically you just build the project by `nim c <myProject.nim>`, since Nim has such a strong macro system a lot of typical build stuff is just done with macros. Of course there's also the default Nimble package manager which allows you to list dependencies and tasks using Nim itself. This means that if you know how to write Nim managing the build system is a breeze.
Ugh, I just got done spending months fighting CMake before moving back to a position using Nim!
You can also compile C projects with Nim like bearssl [1]. Nim takes care to compile the C files and recompile them when config flags change. It's actually really nice.