nall: add support for LoongArch architecture

[212dandan]

Compiling ares project failed in the my local loongarch64 environment.
There are 2 architecture-related errors are reported, for examples,

Q1: unknown arch, please specify manually.
root@localhost:/home/remine/ares/git/ares# make -j4
make[1]: Entering directory “/home/remine/ares/git/ares/desktop-ui”
../nall/GNUmakefile:137: *** unknown arch, please specify manually.。 停止。
make[1]: Leaving directory “/home/remine/ares/git/ares/desktop-ui”

Q2：error "unable to detect architecture".
In file included from ../nall/platform.hpp:3,
                 from ../thirdparty/sljitAllocator.cpp:3:
../nall/intrinsics.hpp:289:4: error: #error "unable to detect architecture"
  289 |   #error "unable to detect architecture"
      |    ^~~~~

Please review.
If you have any questions, you can contact me at any time.

[LukeUsher]

Our recompiler backend (sljit) doesn't appear to support the longarch architecture, so you should not include it in this supported variable.

See https://zherczeg.github.io/sljit/

[LukeUsher]

Although I see the mips64 backend might be compatible due to the fact longarch is derived from it; were you able to test a recompiler based system (n64, ps1)

[sp1187]

Although inspired by MIPS (and RISC-V), LoongArch is not binary compatible. However, it seems like sljit has added a LoongArch backend, see https://github.com/zherczeg/sljit/blob/master/sljit_src/sljitNativeLOONGARCH_64.c. No idea how stable that backend is.