Hi,

When attempting to build luajit on powerpc64le-linux, you will get
errors like this:

--8<---------------cut here---------------start------------->8---
==== Building LuaJIT 2.1.0-beta3 ====
make -C src
make[1]: Entering directory '/tmp/guix-build-luajit-2.1.0-beta3.drv-0/LuaJIT-2.1.0-beta3/src'
lj_arch.h:428:2: error: #error "No support for PowerPC 64 bit mode (yet)"
  428 | #error "No support for PowerPC 64 bit mode (yet)"
      |  ^~~~~
lj_arch.h:428:2: error: #error "No support for PowerPC 64 bit mode (yet)"
  428 | #error "No support for PowerPC 64 bit mode (yet)"
      |  ^~~~~
lj_arch.h:428:2: error: #error "No support for PowerPC 64 bit mode (yet)"
  428 | #error "No support for PowerPC 64 bit mode (yet)"
      |  ^~~~~
lj_arch.h:428:2: error: #error "No support for PowerPC 64 bit mode (yet)"
  428 | #error "No support for PowerPC 64 bit mode (yet)"
      |  ^~~~~
lj_arch.h:428:2: error: #error "No support for PowerPC 64 bit mode (yet)"
  428 | #error "No support for PowerPC 64 bit mode (yet)"
      |  ^~~~~
lj_arch.h:428:2: error: #error "No support for PowerPC 64 bit mode (yet)"
  428 | #error "No support for PowerPC 64 bit mode (yet)"
      |  ^~~~~
lj_arch.h:428:2: error: #error "No support for PowerPC 64 bit mode (yet)"
  428 | #error "No support for PowerPC 64 bit mode (yet)"
      |  ^~~~~
lj_arch.h:428:2: error: #error "No support for PowerPC 64 bit mode (yet)"
  428 | #error "No support for PowerPC 64 bit mode (yet)"
      |  ^~~~~
lj_arch.h:428:2: error: #error "No support for PowerPC 64 bit mode (yet)"
  428 | #error "No support for PowerPC 64 bit mode (yet)"
      |  ^~~~~
lj_arch.h:428:2: error: #error "No support for PowerPC 64 bit mode (yet)"
  428 | #error "No support for PowerPC 64 bit mode (yet)"
      |  ^~~~~
lj_arch.h:428:2: error: #error "No support for PowerPC 64 bit mode (yet)"
  428 | #error "No support for PowerPC 64 bit mode (yet)"
      |  ^~~~~
lj_arch.h:428:2: error: #error "No support for PowerPC 64 bit mode (yet)"
  428 | #error "No support for PowerPC 64 bit mode (yet)"
      |  ^~~~~
lj_arch.h:428:2: error: #error "No support for PowerPC 64 bit mode (yet)"
  428 | #error "No support for PowerPC 64 bit mode (yet)"
      |  ^~~~~
lj_arch.h:428:2: error: #error "No support for PowerPC 64 bit mode (yet)"
  428 | #error "No support for PowerPC 64 bit mode (yet)"
      |  ^~~~~
lj_arch.h:428:2: error: #error "No support for PowerPC 64 bit mode (yet)"
  428 | #error "No support for PowerPC 64 bit mode (yet)"
      |  ^~~~~
lj_arch.h:428:2: error: #error "No support for PowerPC 64 bit mode (yet)"
  428 | #error "No support for PowerPC 64 bit mode (yet)"
      |  ^~~~~
lj_arch.h:428:2: error: #error "No support for PowerPC 64 bit mode (yet)"
  428 | #error "No support for PowerPC 64 bit mode (yet)"
      |  ^~~~~
lj_arch.h:428:2: error: #error "No support for PowerPC 64 bit mode (yet)"
  428 | #error "No support for PowerPC 64 bit mode (yet)"
      |  ^~~~~
lj_arch.h:428:2: error: #error "No support for PowerPC 64 bit mode (yet)"
  428 | #error "No support for PowerPC 64 bit mode (yet)"
      |  ^~~~~
make[1]: *** No rule to make target 'vm_ppc64.dasc', needed by 'host/buildvm_arch.h'.  Stop.
make[1]: Leaving directory '/tmp/guix-build-luajit-2.1.0-beta3.drv-0/LuaJIT-2.1.0-beta3/src'
make: *** [Makefile:113: default] Error 2
--8<---------------cut here---------------end--------------->8---

This has downstream impacts, such as being unable to build LuaJITTeX.
If we can't use LuaJIT on powerpc64le-linux, we should probably remove
it from the luajit package's list of supported systems.

I checked their email list and website, but I can't find information
about whether the LuaJIT project is actively working on support for
powerpc64le architecture specifically.  I'll ask their email list
(luajit@freelists.org) in a moment, and we'll see what they say.

-- 
Chris