This is not needed, since `hscolour` has no output to `/etc`, and it
breaks certain old builds (see https://hydra.nixos.org/build/57925511)
because the older cabal used does not understand this flag.
- The haskell lib is very close to not relying on Nixpkgs. I think
this is good---simpler to think about and matches Nixpkgs's lib.
- The haskell lib is only imported once
- stdenv is exposed more shallowly so it can be overriden more easily.
I'll eventually use this on Darwin to avoid the Sierra shared
library problems (unless changes are to be made system-wide).
Closes https://github.com/NixOS/nixpkgs/pull/27840.
We want code such as `(pkg.override {}).overrideScope (self: super: {})` to
work. This didn't work before, since `override` will call the original package
again, and the attribute `overideScope`, which `callPackageWithScope` added,
wasn't added again. The fix for this is to modify the package function itself
to include the `callPackageWithScope` attribute, so it'll be re-added whenever
the function is overriden for with arguments.
There is a small problem here though: since callPackage uses some magic
(`builtins.functionArgs`) to determine the auto-arguments of a function, we
can't just write `callPackageWith scope drvScope`, since
`builtins.functionArgs drvScope` will be `{}`. To fix this, we implement our own
`callPackageWith`.
Fixes https://github.com/NixOS/nixpkgs/issues/7953.
Closes https://github.com/NixOS/nixpkgs/pull/9336.
