Until it's fixed, you can add an overlay to disable the checkPhase.
Something like this ought to work:

diffutils = super.diffutils.overrideAttrs (old: {
  doCheck = false;
});

In reply to @hive:the-apothecary.club
ugh same issue with gnugrep after 2 hours

for path in (nix path-info --all)
  set deriver (nix-store --query --deriver $path)
  if test $deriver != "unknown-deriver"
    echo "Checking $path..."
    echo "Deriver: $deriver"
    set system (nix derivation show "$deriver"^'*' | grep "\"system\":")
    echo "System: $system"
    if string match -q "*\"system\": \"riscv64-linux\"" $system
      echo "Pushing $path to riscv64-ghc-cache..."
      cachix push riscv64-ghc-cache $path
      echo "Done pushing $path to riscv64-ghc-cache."
    else
      echo "$path is not built for riscv64-linux."
    end
  end
end

In reply to @alex:tunstall.xyz
It really sounds like there's something wrong with your system/emulator.
(diffutils builds fine for me.)

Given that you can reproduce on multiple x86 machines, it looks like:

native riscv => ok
emulated riscv => failure

I'm running the build emulated locally to be extra sure of the above.

I'm not really sure how Nixpkgs handles fixes for emulator-only issues.
(It could also just be that my RISC-V hardware is more forgiving than QEMU of non-standard behaviour?)

In reply to @0x4a6f:matrix.org