survey: Fix returned haskellPackages not being overridable

[nh2]

So far, staticHaskellBinariesOverlay just did mapAttrs over haskellPackages directly.

That is wrong.

It should do a proper haskellPackages.override, just like haskellLibsReadyForStaticLinkingOverlay does, and so its mapAttrs over super instead.

This commit does that.

Because of this bug, it was until now impossible to further override the returned haskellPackages. For example, using

static_haskellPackages_with_fixes =
  static-stack2nix-builder.haskell-static-nix_output.haskellPackages.override (old: {
    # composeExtensions boilerplate here ...
     {
       # Haskell overrides here
     }
});

(as is sometimes necessary for the static-stack2nix-builder to override one's own packages) would not work; as soon as .override was used, all packages inside would lose their static overrides, e.g. configureFlags would be reset to "".

[nh2]

CI build turned up a couple unrelated problems:

• https://github.com/vincenthz/hs-tls/issues/413 (QuickCheck test failure)
  • Solved, due to 10 seconds timeout for test that was exceeded under load.
• https://github.com/peti/cabal2spec/commit/6078778c06be45eb468f4770a3924c7be190f558#commitcomment-36904932 (date-dependent test failure)
  • Solved with https://github.com/nh2/static-haskell-nix/pull/74/commits/db079b13d40cedc11c4b8bd89efa471b3235cae8

[nh2]

CI green, merging.