I get this error when the Rust toolchain tries to compile the troublesome compiler-rt LLVM package using the RISC-V GNU toolchain gcc (riscv64-unknown-elf-gcc). It looks like gcc doesn't recognize this flag; it's a clang flag. I'm not sure why LLVM insists on passing it to gcc. And I can't find a way to disable it without patching LLVM.

For now the patch works fine, but it would be nice to remove this. Maybe we can switch to clang, but the pre-packaged RISC-V toolchains that we're using only include gcc. Some possibly useful resources:

• https://stackoverflow.com/questions/68580399/using-clang-to-compile-for-risc-v
• https://github.com/riscv-collab/riscv-gnu-toolchain?tab=readme-ov-file#llvm--clang
• https://reviews.llvm.org/D43105