testing/gcc-cross-embedded-stage1: Add riscv-none-elf and upgrade to 10.2.0
This MR contains three commits. The first does some clean up. The second adds the subpackage gcc-riscv-none
for embedded RISC-V development. The last upgrades to version 10.2.0.
A single MR for all changes reduces the required build time, which sadly is quite significant.
Edited by Marian Buschsieweke