cargo-zigbuild

Zig also takes this approach, and even exposes its C compiler (which if I recall correctly is basically Clang plus diverse sysroots and other customisation out of the box) as a separate `zig cc`. I do a lot of work in Rust, and cross-compilation can be a pain when you have a lot of C dependencies. Fortunately https://github.com/messense/cargo-zigbuild exists. It sounds crazy, but using Zig's inbuilt C compiler to help build my Rust projects has been the smoothest option I've found. I can't help but wonder if it would be worth it for Rust to follow D and Zig by shipping its own inbuilt C compiler, even if they still want to also support external C toolchains. It should be roughly the same effort as it was for Zig, given that they both use LLVM.

Have you tried cargo zigbuild? You can target specific GLIBC versions. https://github.com/messense/cargo-zigbuild