New package: cross-riscv64-none-elf-0.1

[kuwoyuki]

GCC toolchain targeting bare-metal RISC-V systems (riscv64-none-elf)

Testing the changes

• I tested the changes in this PR: YES

New package

• This new package conforms to the package requirements: YES

Local build testing

• I built this PR locally for my native architecture, (x86_64-glibc)

[sgn]

Why do we need cross-riscv64-none-elf-gcc-bootstrap?