add loong64 support

[yzewei]

Provides the Loongarch architecture to support the S5CMD project.
The LoongArch architecture (LoongArch) is an Instruction Set Architecture (ISA) that has a RISC style.

One of the most important thing is there is a docker image where s5cmd tests can be done. You can use it on x86 machine with docker run -it --rm merore/archlinux-loongarch64.
About this image:

• Boot an Loongarch64-based Arch Linux with qemu-system-loongarch64
• The default user/password is root/loongarch64
• All dependcies required by criu build and test are pre-installed
• You must configure your own dependence on the environment, Golang's installation package is located at http://ftp.loongnix.cn/toolchain/golang/go-1.20/abi2.0/go1.20.2.linux-loong64.tar.gz

[yzewei]

@igungor @nelhage Please~