Fix/riscv gcc toolchain

[wohali]

The riscv gcc toolchain has migrated from riscv-none-embed-* binaries to riscv-none-elf-* names.

https://github.com/xpack-dev-tools/riscv-none-embed-gcc-xpack#deprecated-replaced-by-xpack-dev-toolsriscv-none-elf-gcc-xpack

This toolchain is now end-of-life and there will be no more releases.

Please update your projects to use the new xpack-dev-tools/riscv-none-elf-gcc-xpack.