memtest86plus: fix, switch to using coreboot's branch

[oxij]

Motivation for this change

It failed to work on my Thinkpad X230. This fixes it both with Lenovo BIOS and with coreboot. I think the first patch should be backported to 18.03.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option build-use-sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • other Linux distributions
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.

[GrahamcOfBorg]

No attempt on aarch64-linux (full log)

The following builds were skipped because they don't evaluate on aarch64-linux: memtest86plus

Partial log (click to expand)

a) For `nixos-rebuild` you can set
  { nixpkgs.config.allowUnsupportedSystem = true; }
in configuration.nix to override this.

b) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
  { allowUnsupportedSystem = true; }
to ~/.config/nixpkgs/config.nix.

[GrahamcOfBorg]

Success on x86_64-linux (full log)

Attempted: memtest86plus

Partial log (click to expand)

as -32   -o setup.pre.o setup.pre.s
ld -z max-page-size=0x1000 -T memtest.bin.lds bootsect.pre.o setup.pre.o -b binary \
memtest_shared.bin -o memtest.bin
installing
post-installation fixup
shrinking RPATHs of ELF executables and libraries in /nix/store/943rdxs64wdbbk4ci1gqzrgq8fdrjrqn-memtest86+-5.01+coreboot-20180113
strip is /nix/store/j75dgadrff2d1fyc4fczmcgqkid2imdx-binutils-2.30/bin/strip
patching script interpreter paths in /nix/store/943rdxs64wdbbk4ci1gqzrgq8fdrjrqn-memtest86+-5.01+coreboot-20180113
checking for references to /build in /nix/store/943rdxs64wdbbk4ci1gqzrgq8fdrjrqn-memtest86+-5.01+coreboot-20180113...
/nix/store/943rdxs64wdbbk4ci1gqzrgq8fdrjrqn-memtest86+-5.01+coreboot-20180113

[oxij]

Thanks! Should I make another PR for 18.03 or will you just cherry-pick it?