Add support for LoongArch
We are interested in testing ARCH=loongarch in TuxSuite now that basic support for building LoongArch with LLVM is present in 6.5-rc1, which requires that TuxMake support it first. I think LoongArch is only supported in GCC 12.1.0 and newer and the kernel is only buildable with clang-17 (current clang-nightly) or newer, so it has a narrow versioned toolchain list.
I do not mind looking at implementing this myself if I have some guidance around what needs to be added where. I assume an .ini file will be needed as well as wiring up the Docker containers with the cross compilers; I will need to look and see what is available in Debian.