The Go runtime apparently uses system calls directly. The implementation of every other programming language I know uses the C standard library. Rust has a freestanding mode which is great. I even made a crate for Linux system calls but that needs inline assembly which isn't stable yet.

As for user space projects, I know this one:

https://github.com/arsv/minibase

I meant to start my own but replacing what already exists is a lifetime of work. Haven't had much free time these days nor the willpower to make it happen. I created a liblinux but it's incomplete:

https://github.com/matheusmoreira/liblinux

I also found out the Linux kernel itself has an excellent system call stubs header which they apparently use for their own tools:

https://github.com/torvalds/linux/blob/master/tools/include/...

Go does syscalls directly on Linux. Libc is only needed if you use a thing that only exists in libc (e.g. NSS).

In matter of scheme you have the guile project. https://www.gnu.org/software/guile/guile.html