Initial support for foreign architectures (i686 and aarch64).

[maleadt]

Replaces #144; cc @IanButterworth @DilumAluthge
Fixes #97

Tested that this works by installing qemu-user-static and whatever binfmt-integration package your distro uses:

julia> config = Configuration(julia="1.9-alpha1", arch="aarch64")

julia> result = PkgEval.evaluate_test(config, Package(;name="Example"))

julia> println(result.log)
Package evaluation of Example started at 2022-12-10T20:59:20.579

Julia Version 1.9.0-alpha1
Commit 0540f9d7394 (2022-11-15 14:37 UTC)
Platform Info:
  OS: Linux (aarch64-linux-gnu)
  CPU: 32 × AMD Ryzen 9 5950X 16-Core Processor
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-14.0.6 (ORCJIT, generic)
  Threads: 1 on 32 virtual cores
Environment:
  JULIA_DEPOT_PATH = ::/usr/local/share/julia
  JULIA_PKGEVAL = true

...

Testing completed after 0.0s

PkgEval succeeded

Although that's pretty neat, emulation is way slower than I expected:

julia> config = Configuration(julia="1.9-alpha1", arch="aarch64")
julia> @time result = PkgEval.evaluate_test(config, Package(;name="Example"))
 44.638430 seconds (3.41 M allocations: 338.130 MiB, 0.26% gc time, 1.06% compilation time: 32% of which was recompilation)

julia> config = Configuration(julia="1.9-alpha1")
julia> @time result = PkgEval.evaluate_test(config, Package(;name="Example"))
  4.488381 seconds (6.57 k allocations: 634.000 KiB, 0.00% compilation time)

I originally also wanted to integrate PkgEval.jl with Qemu_jll.jl and automatically use qemu's user-mode emulation, but turns out it doesn't actually handle execve, so we need to use binfmt for transparent emulation. But since it's way too slow for actual PkgEval purposes, I won't explore that any further anyway.

Finally, as you see in the output above cpu_time reporting doesn't work properly in the case of qemu emulation, but I assume it does with native aarch64 execution, so that shouldn't hold this PR back.

[maleadt]

If we ever want to make emulation transparent without requiring binfmt, we'd need to add something like https://patchwork.ozlabs.org/project/qemu-devel/patch/1455515507-26877-1-git-send-email-petrosagg@resin.io/ to our Qemu_jll.

[maleadt]

If we ever want to make emulation transparent without requiring binfmt, we'd need to add something like https://patchwork.ozlabs.org/project/qemu-devel/patch/1455515507-26877-1-git-send-email-petrosagg@resin.io/ to our Qemu_jll.

Well, I've implemented that.