This is broken on aarch64-linux / x86_64-darwin, so might as well just disable it for now.

Forward the experimental features to the nix repl subprocesses

Pass the current experimental features using `NIX_CONFIG` to the various
Nix subprocesses that `nix repl` invokes.

This is quite a hack, but having `nix repl` call Nix with a subprocess
is a hack already, so I guess that’s fine.

Keep the `isFlake` attribute for overriden inputs

When overriding an input that isn’t a flake, mark the override as also not
being a flake.

Fix #3774

Fix gc crash

Add armv6l-linux & armv7l-linux as cross jobs

flake.lock: Update

Flake input changes:

* Updated 'nixpkgs': 'github:NixOS/nixpkgs/bb8a5e54845012ed1375ffd5f317d2fdf434b20e' -> 'github:NixOS/nixpkgs/f77036342e2b690c61c97202bf48f2ce13acc022'

man: fix formatting of nix3-profile-remove

Eventually delete the CA paths lock files

Make the CA tests actually test something

Fixes

  error: cannot create symlink '/home/eelco/Dev/nix/tests/result'; already exists

Fixes the problem where a stack pointer outside the original
thread causes the collector to crash.

It could be made more accurate by recording the stack pointer
every time we switch to a coroutine. We can use this information
to update our own coroutine stacks like normal data. When the
stack pointer is on a thread, we can add a field to GC_thread
"fallback_sp" to be used when the thread sp is outside the original
thread range.

Mark the lockfiles as having to eventually be deleted so that they don’t
stay laying around in the store at the end of the build

Fix #4936

Make CA derivations compatible with recursive Nix

Add an access-control list to the realisations in recursive-nix (similar
to the already existing one for store paths), so that we can build
content-addressed derivations in the restricted store.

Fix #4353

This fixes a crash that looks like:

```
Thread 1 "nix-build" received signal SIGSEGV, Segmentation fault.
0x00007ffff7ad22a0 in GC_push_all_eager () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1
(gdb) bt
0  0x00007ffff7ad22a0 in GC_push_all_eager () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1
1  0x00007ffff7adeefb in GC_push_all_stacks () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1
2  0x00007ffff7ad5ac7 in GC_mark_some () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1
3  0x00007ffff7ad77bd in GC_stopped_mark () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1
4  0x00007ffff7adbe3a in GC_try_to_collect_inner.part.0 () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1
5  0x00007ffff7adc2a2 in GC_collect_or_expand () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1
6  0x00007ffff7adc4f8 in GC_allocobj () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1
7  0x00007ffff7adc88f in GC_generic_malloc_inner () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1
8  0x00007ffff7ae1a04 in GC_generic_malloc_many () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1
9  0x00007ffff7ae1c72 in GC_malloc_kind () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1
10 0x00007ffff7e003d6 in nix::EvalState::allocValue() () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
11 0x00007ffff7e04b9c in nix::EvalState::callPrimOp(nix::Value&, nix::Value&, nix::Value&, nix::Pos const&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
12 0x00007ffff7e0a773 in nix::EvalState::callFunction(nix::Value&, nix::Value&, nix::Value&, nix::Pos const&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
13 0x00007ffff7e0a91d in nix::ExprApp::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
14 0x00007ffff7e0a8f8 in nix::ExprApp::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
15 0x00007ffff7e0e0e8 in nix::ExprOpNEq::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
16 0x00007ffff7e0d708 in nix::ExprOpOr::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
17 0x00007ffff7e0d695 in nix::ExprOpOr::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
18 0x00007ffff7e0d695 in nix::ExprOpOr::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
19 0x00007ffff7e0d695 in nix::ExprOpOr::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
20 0x00007ffff7e0d695 in nix::ExprOpOr::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
21 0x00007ffff7e09e19 in nix::ExprOpNot::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
22 0x00007ffff7e0a792 in nix::EvalState::callFunction(nix::Value&, nix::Value&, nix::Value&, nix::Pos const&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
23 0x00007ffff7e8cba0 in nix::addPath(nix::EvalState&, nix::Pos const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, nix::Value*, nix::FileIngestionMethod, std::optional<nix::Hash>, nix::Value&)::{lambda(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)#1}::operator()(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) const () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
24 0x00007ffff752e6f9 in nix::dump(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, nix::Sink&, std::function<bool (std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)>&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixutil.so
25 0x00007ffff752e8e2 in nix::dump(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, nix::Sink&, std::function<bool (std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)>&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixutil.so
26 0x00007ffff752e8e2 in nix::dump(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, nix::Sink&, std::function<bool (std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)>&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixutil.so
27 0x00007ffff752e8e2 in nix::dump(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, nix::Sink&, std::function<bool (std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)>&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixutil.so
28 0x00007ffff752e8e2 in nix::dump(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, nix::Sink&, std::function<bool (std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)>&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixutil.so
29 0x00007ffff752e8e2 in nix::dump(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, nix::Sink&, std::function<bool (std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)>&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixutil.so
30 0x00007ffff757f8c0 in void boost::context::detail::fiber_entry<boost::context::detail::fiber_record<boost::context::fiber, nix::VirtualStackAllocator, boost::coroutines2::detail::pull_coroutine<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >::control_block::control_block<nix::VirtualStackAllocator, nix::sinkToSource(std::function<void (nix::Sink&)>, std::function<void ()>)::SinkToSource::read(char*, unsigned long)::{lambda(boost::coroutines2::detail::push_coroutine<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >&)#1}>(boost::context::preallocated, nix::VirtualStackAllocator&&, nix::sinkToSource(std::function<void (nix::Sink&)>, std::function<void ()>)::SinkToSource::read(char*, unsigned long)::{lambda(boost::coroutines2::detail::push_coroutine<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >&)#1}&&)::{lambda(boost::context::fiber&&)#1}> >(boost::context::detail::transfer_t) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixutil.so
31 0x00007ffff6f331ef in make_fcontext () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libboost_context.so.1.69.0
32 0x0000000000000000 in ?? ()
```

Make the post-build-hook also run for unresolved CA derivations

Fix #4837

Broken by https://github.com/NixOS/nix/issues/4936

Fix a mistake in config.nix that was preventing
`NIX_TESTS_CA_BY_DEFAULT` from having any meaningful effect

Gracefully handle duplicate realisations

Make `nix develop` work with CA derivations

Should always hold, but that’s not necessarily obvious, so better
enforce it

Make `nix-shell` support content-addressed derivations

Recursively substitute the realisations