lib/systems/platforms.nix: use "32" instead of "o32" for mips32 ABI

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Description of changes

There is only one ABI for 32-bit MIPS chips. Before mips64, it didn't really have a name.

The 64-bit MIPS ABI comes in two flavors, "n64" and "n32". It is commonplace to refer to the old 32-bit ABI as "o32" (MIPS and SGI documents do this).

However, when configuring gcc, one must use --with-abi=32, not --with-abi=o32.

Let's keep GCC happy with this commit.

Things done

• Built on platform(s)
  • mips64el-linux
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.

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Ping...

This is a pretty low-risk merge.

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Ping

[vcunat]

OK, this seems like a step forward, but locally it's not a full success for me:

$ nix build -f pkgs/top-level/release-cross.nix bootstrapTools.mipsel-linux-gnu.bootstrapTools
error: builder for '/nix/store/nvl5dzg752jzrpnan9c0chv9rpd2i77y-bootstrap-tools.drv' failed with exit code 1;
       last 2 log lines:
       > 
       > ErrorErrorhexecuting '/nix/store/ywbgw67hrx1yj6kcg8d77nnyf987dwkw-busybox': Exec format error

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nix build -f pkgs/top-level/release-cross.nix bootstrapTools.mipsel-linux-gnu.bootstrapTools

I'm running this now at master but it will be an hour or two before it gets caught up.

[ghost]

I think this might be more fallout from #168650 if this works for you:

nix build -f . pkgsCross.mipsel-linux-gnu.stdenvBootstrapTools.build

That's what I was testing with.

Once my build gets caught up I'll check, and make sure that #183072 fixes it. (Edit: this is unrelated to #168650 / #183072)

[vcunat]

Yes, that does succeed (cached from the attempt above apparently). My command above only fails in the very last build step.

[ghost]

My command above only fails in the very last build step.

Oh, in that case it isn't #168650, and I think Hydra will be fine (but still checking anyways -- about halfway built).

I seem to recall running into that error before... release-cross.nix is pretty convoluted, but it boiled down to bootstrapTools being an attrset-of-derivations, one of which tries to execute the tools.

[ghost]

Yeah Hydra will be fine.

nix@moore:/git/nixpkgs$ nix-instantiate pkgs/top-level/release-cross.nix -A bootstrapTools.mipsel-linux-gnu
/nix/store/b6d509dr6anhc46q7ggnzkcn2a7dpfbn-binutils-mipsel-unknown-linux-gnu-2.38.drv
/nix/store/d3q6wxfsfqdqz66rykrmfdrym8yac7sp-gcc-debug-mipsel-unknown-linux-gnu-10.4.0.drv
/nix/store/g2aii8hfmy18xjagbip25p9sigxjic5c-stdenv-bootstrap-tools-mipsel-unknown-linux-gnu.drv
/nix/store/wsgr73yzvjmj7rcg6izvv1iml998bcpg-busybox-mipsel-unknown-linux-gnu-1.35.0.drv
/nix/store/xk24cqi2fns7shi2xi7nwh3g7rqzyvkg-coreutils-mipsel-unknown-linux-gnu-9.1.drv
/nix/store/1292868idj07b8qmagk4qyq11ygqy6wj-stdenv-bootstrap-tools-mipsel-unknown-linux-gnu.drv
/nix/store/n50lqs93nxr3kffmw5z19ar0r1rgh3zd-gnutar-mipsel-unknown-linux-gnu-1.34.drv
/nix/store/nvl5dzg752jzrpnan9c0chv9rpd2i77y-bootstrap-tools.drv
/nix/store/j8c9bjpxdijpl56k93y34qz66jn0fbjq-test-bootstrap-tools.drv

(I reordered the lines above) The last two derivations can only be built on host==build.

However this will work:

nix-instantiate pkgs/top-level/release-cross.nix -A bootstrapTools.mipsel-linux-gnu | grep -v 'tools.drv' | xargs nix build -L

Also,

nix show-derivation /nix/store/j8c9bjpxdijpl56k93y34qz66jn0fbjq-test-bootstrap-tools.drv | grep system
    "system": "mipsel-linux",
      "system": "mipsel-linux"

I think there's something in the hydraJob machinery that makes sure it skips jobs where drv.system!=builtins.currentSystem since these can never be expected to work correctly.

[ghost]

Yeah Hydra will be fine.

All good!