Reverts the bug introduced by
https://github.com/NixOS/nixpkgs/pull/34939

The closure gets a bit big otherwise.

Tests are generally very lightweight (or at least should be), so it doesn’t make
sense to contact a substituter first.

The setup of environment variables can be used by other tests to set up a local
environment for nix invocations.
Preparation for use in package-tests.

All functions are currently fixed to time out after 899 seconds, which is a bit
long in most cases.

- split outputs (doc, man, out)
- a new runtime dependency on getconf
- fix up SCRIPTS_DIR in wrapper
- clean output folder of stray doc files
- add license & maintainer

Tested with `nixos/tests/rabbitmq.nix`, inside a docker image and manually.

- [x] passes nixos/tests/rabbitmq.nix

A new call to the getconf utility made the test fail, this has been patched.

Modules can now add the extra input attribute `testing` to get access to the
VM-testing functionality (qemu nixos VM that runs a perl testing DSL).

An option for keeping module tests close to the modules they belong to.

Makes it possible to have arbitrarily deeply nested structures. Requisite for
creating a `tests` option.

withTests is just a small wrapper around the more abstract functions `drvSeq`
and `drvSeqL`, which act as `seq` for derivations.
It might be possible to make them even more abstract by not requiring (some of)
their arguments to be derivations, but this is a nice first step.

Maybe the functions should move to `lib/trivial` instead?

The idea is that you can test derivations without having to rebuild if a test
fails or needing a VM-test.

So
foo = withTests { t1 = ''exit 1''; } fooDrv
will build fooDrv, but fail the build of foo because test t1 exits ≠ 0.

This is the base building block for a nixpkgs testing framework with no nixos
dependency.

This means the generation of values can now be influenced, even down from e.g.
an INI generator.
Breaks the interface of `mkKeyValueDefault` to match its interface to other
generator functions. It might me sensible to rename `mkKeyValue` and
`mkKeyValueSet` to conform to the `toX`-style of generator functions.

Re-apply patch originally introduced in 23da6f9c ("mailutils: fix
for sendmail path"), fixing regression introduced in 27a9ef87
("mailutils: fix build break").

Fixes #21008.
Closes #38708.

[Bjørn: modify/extend commit message.]

(cherry picked from commit b2b44c9e9fbcfe1215cceec68a062e1fbbd80710)

Sierra hack

[18.03]: haskellPackages: disable some failing hydra builds

Also fix numberous bugs, such as:

 - Not getting confused on more flags taking file arguments.

 - Ensuring children reexport their children, but the original
   binary/library doesn't.

 - Not spawning children when it turns out we just dynamically link
   under the threshold but our total number of inputs exceeeds it.

 - Children were always named `libunnamed-*`, when that name was
   supposed to be the last resort only.

ld-wrapper's own RPATH check hardcodes `.so`, but darwin uses `.dylib`
*and* (in practice due to lousy build systems) `.so`. We don't care
however because we never inject `--rpath` like that in practice on
Darwin. Hopefully someday we won't on linux either.

for fsnotify-conduit, powerqueue-distributed, rocksdb-haskell

(cherry picked from commit da8fc391a0897a3897630ce322ad19a825a4ac93)

(cherry picked from commit fddb1457b04e6c5700c6a30cbf349c0511bdb62d)

(cherry picked from commit ee7e6cdbaddd370fb758b45e7af2a9574d344786)

(cherry picked from commit 32d620d7397ccc3435c7f6390b788f5da2703b65)

(cherry picked from commit 909d90d6a8804a0cd2d4e39531503356a10db6ab)

(cherry picked from commit 3b0180fb95493d6afbf535dafcdaa77859019295)

(cherry picked from commit 98270cb95939600f26f227fc40c73406b91c4d94)

(cherry picked from commit 49d0fa77293ecf2cab218113b22bb74b2af7e9e2)

also fixes #34854 and correct license to GPL3

(cherry picked from commit 35049f9e61dd4e87413d137122cced4764f50f2f)

(cherry picked from commit ed6f1761ccbd8635a9c53dd7743b656d5f60d62c)

spotify: 1.0.72.117 -> 1.0.77.338

(cherry picked from commit e9e823c178d70b8562094ee07786e7483952919b)

fixes #38859

(cherry picked from commit 6b796a9c23db8cbb3065ffdd20c1a53fd86de9a6)

Source master rebase of my [PR #34].

Eventually, we might consider doing something for GNU binutils too, in
order that we switch (the normal) ld-wrapper to always use this to
leverage ld to resolve libraries, rather than faking it in bash.

[PR #34]: https://github.com/tpoechtrager/cctools-port/pull/34

This more politely expresses the same thing

exportReferencesGraph is deprecated and doesn't have the generated
initial Nix database contain the SHA256 of the contents of the store
paths, which breaks various things under Nix 2.0.

(cherry picked from commit 487be791d783c706369a1a0740e03a0bb60d8f1f)

Semi-automatic update generated by https://github.com/ryantm/nixpkgs-update tools.

This update was made based on information from https://repology.org/metapackage/pick/versions.

These checks were done:

- built on NixOS
- ran ‘/nix/store/mr0512zhzbbarb99l6v31pgsw1f8k859-pick-2.0.2/bin/pick -h’ got 0 exit code
- ran ‘/nix/store/mr0512zhzbbarb99l6v31pgsw1f8k859-pick-2.0.2/bin/pick -v’ and found version 2.0.2
- found 2.0.2 with grep in /nix/store/mr0512zhzbbarb99l6v31pgsw1f8k859-pick-2.0.2
- directory tree listing: https://gist.github.com/797cf336b38181f76cab1e08936713b1

(cherry picked from commit ab96418801c67e08442560834359909695502e08)

(cherry picked from commit d1dfe27ad9d4e7acb4c3ba6382e4526b33ed3552)

(cherry picked from commit 2bb811c6a0a4817d3394f0887331485d95f1c25e)