I recently tried to compile a Rust program for the enwikt-translations tool and found that I couldn't compile the new version of rlua library (Rust high-level bindings to Lua). It used to compile just fine on the toolservers, but it now generates bindings with rust-bindgen, which requires clang. (Hopefully someday support for GCC will be added, but it's not here yet.) It gives a dumb error about not being able to find stdarg.h, which is in the GCC package. I fixed that on my own computer with sudo apt install clang.
Could clang be installed?