Alternately, python cryptography could have chosen a different memory safe language, like Go, which is supported by GCC. Why did they intentionally choose a poorly fit language like Rust? Use the best tool for the job, yes?
The main benefit of a GCC-based Rust compiler would be disentangling Rust from rustc, specification from implementation.
LLVM has changed the situation quite a bit though. GCC could make itself easier to hack on but it might be too late.
It's arguably true that RMS's zealotry actually backfired spectacularly.
I think it's probably for the best; having two competing solutions with different priorities is probably a win for everyone, gcc and clang users alike. gcc has improved much in the last few years in part due to LLVM/clang's pressure.
I've seen people bring this up a few years ago, but there wasn't much change in attitude on rms' end. I don't keep up on the day-to-day of gcc, so perhaps things changed in the last few years(?) I would be surprised if this would happen under rms' tenure though.