pythonPackages.xgboost: fix build

[Ma27]

Motivation for this change

Fixes the broken path detection of the xgboost python package and replaces it with a simple path that substitutes the storepath of libxgboost.so.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• 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/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Fits CONTRIBUTING.md.

---

[Ma27]

will run nox-review just to be sure.

[Ma27]

Result in /tmp/nox-review-in4b42yn
total 8
lrwxrwxrwx 1 ma27 users 66 Jul 19 13:36 result -> /nix/store/dpc92c1w1h7zc9yjav9v8ih3f3j3jb4m-python2.7-xgboost-0.72
lrwxrwxrwx 1 ma27 users 56 Jul 19 13:36 result-2 -> /nix/store/dni9473cw0bh335ps0gz5778ybwa5qyj-xgboost-0.72
lrwxrwxrwx 1 ma27 users 66 Jul 19 13:36 result-3 -> /nix/store/g7jplykqbpgi8nnqicfrljk0b4g25721-python3.6-xgboost-0.72

[GrahamcOfBorg]

No attempt on aarch64-linux (full log)

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

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: xgboost

Partial log (click to expand)

installing
post-installation fixup
shrinking RPATHs of ELF executables and libraries in /nix/store/dni9473cw0bh335ps0gz5778ybwa5qyj-xgboost-0.72
shrinking /nix/store/dni9473cw0bh335ps0gz5778ybwa5qyj-xgboost-0.72/lib/libxgboost.so
shrinking /nix/store/dni9473cw0bh335ps0gz5778ybwa5qyj-xgboost-0.72/bin/xgboost
strip is /nix/store/90vmpr41dzsx350k5argycaf693hnl1l-binutils-2.30/bin/strip
stripping (with command strip and flags -S) in /nix/store/dni9473cw0bh335ps0gz5778ybwa5qyj-xgboost-0.72/lib  /nix/store/dni9473cw0bh335ps0gz5778ybwa5qyj-xgboost-0.72/bin
patching script interpreter paths in /nix/store/dni9473cw0bh335ps0gz5778ybwa5qyj-xgboost-0.72
checking for references to /build in /nix/store/dni9473cw0bh335ps0gz5778ybwa5qyj-xgboost-0.72...
/nix/store/dni9473cw0bh335ps0gz5778ybwa5qyj-xgboost-0.72