[Libguestfs] Please add support for LoongArch architecture.

Dear developers, Please add support for LoongArch architecuture . The LoongArch architecture (LoongArch) is an Instruction Set Architecture (ISA) that has a RISC style. Documentations: ISA: https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html ABI: https://loongson.github.io/LoongArch-Documentation/LoongArch-ELF-ABI-EN.html More docs can be found at: https://loongson.github.io/LoongArch-Documentation/README-EN.html