add loong64 support

[yzewei]

Protoc temporarily provides Loongarch support, and this submission adds a Protoc supported by Loongarch support.

The LoongArch architecture (LoongArch) is an Instruction Set Architecture (ISA) that has a RISC style.

[yzewei]

@thallgren thanks!

[thallgren]

@yzewei , not a requirement, but is there any way we could add unit tests for this architecture? I don't suppose GitHub as a runner for it.

[yzewei]

Hi, @thallgren

One of the most important thing is there is a docker image where go-fuseftp 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
  Finally, thank you for your patience !

[thallgren]

Thanks for providing this together with info on how it can be tested. Much appreciated.