Rust toolchain for loongarch64

⚠️ The repo is especially prepared for the Arceos project.⚠️

All tested only on Debian-based systems.

The default config.toml file provided in the repo builds the Rust toolchain for the target
x86_64-unknown-linux-gnu, x86_64-unknown-none, riscv64gc-unknown-none-elf, riscv64gc-unknown-linux-gnu,aarch64-unknown-none-softfloat, aarch64-unknown-linux-gnu, loongarch64-unknown-none-softfloat, loongarch64-unknown-none, loongarch64-unknown-linux-gnu.

How to use:

1. Run sudo sh add-apt-dependencies.sh to install required dependencies.
2. Run sudo sh sccache.sh to install sccache, which will accelerate the compiling procedure.
3. Run sh add-loongarch64-unknown-linux-gnu.sh to install loongarch64-unknown-linux-gnu toolchain.
4. Run sh add-riscv64-unknown-elf.sh to install add-riscv64-unknown-elf toolchain.
5. Run sh build-toolchain.sh to download rust source code, and then build & install rust toolchain.

After that, you can find your toolchain at ~/.rustup/toolchains/dev, which should be added to the environment $PATH.