This should resolve the failing build.

See https://github.com/NixOS/nixpkgs/pull/128674 for a better fix.

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

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.

Co-authored-by: Matthew Bauer <mjbauer95@gmail.com>

disable lowdown sandbox on aarch64-darwin

To prevent the OSX build to fail because of a too long socket path

That way we can run them without rebuilding Nix

This requires adding `nix` to its own closure which is a bit unfortunate,
but as it is optional (the test will be disabled if `OUTER_NIX` is unset) it
shouldn't be too much of an issue.

(Ideally this should go in another derivation so that we can build Nix and run
the test independently, but as the tests are running in the same derivation
as the build it's a bit complicated to do so).

When performing distributed builds of machine learning packages, it
would be nice if builders without the required SIMD instructions can
be excluded as build nodes.

Since x86_64 has accumulated a large number of different instruction
set extensions, listing all possible extensions would be unwieldy.
AMD, Intel, Red Hat, and SUSE have recently defined four different
microarchitecture levels that are now part of the x86-64 psABI
supplement and will be used in glibc 2.33:

https://gitlab.com/x86-psABIs/x86-64-ABI
https://lwn.net/Articles/844831/

This change uses libcpuid to detect CPU features and then uses them to
add the supported x86_64 levels to the additional system types. For
example on a Ryzen 3700X:

$ ~/aps/bin/nix -vv --version | grep "Additional system"
Additional system types: i686-linux, x86_64-v1-linux, x86_64-v2-linux, x86_64-v3-linux

This works by using Cachix feature of serving a file from
a store path.

We upgrade to lowdown 0.8.0 [1] which contains a fix/improvement to a
behavior mentioned in this issue thread [2] where a big part of
lowdown's API would just call exit(1) on allocation errors since that
is a satisfying behavior for the lowdown binary.

Now lowdown_term_rndr returns 0 if an allocation error occurred which we
check for in libcmd/markdown.cc.

Also the extern "C" { } wrapper around lowdown.h has been removed as it
is not necessary.

[1]: https://github.com/kristapsdz/lowdown/blob/6ca7c855a063d1c77ae0b89405047cc3913a74d8/versions.xml#L987-L1006
[2]: https://github.com/kristapsdz/lowdown/issues/45#issuecomment-756681153

This fixes the libatomic detection.

This allows patching Nix for Hydra with additional overlays, because
`.overrideAttrs` and co. will persist the passthru's

This allows users to get Nix from Hydra via a stable url like
https://hydra.nixos.org/build/132078238/download/1/nix

The goal is to allow the installation and testing of arbitrary Nix
versions. Extend the base installer to accept a `--tarball-url-prefix
<url>` to change where the Nix tarball is getting downloaded from.

Once this is merged it should allow to:
1. Pick an evaluation at https://hydra.nixos.org/jobset/nix/master that
   looks healthy
2. Select the installedScript build and find the store path.

Now equipped with all of this, use an instance of nar-serve to fetch the
install script and release tarballs:

    curl -sfL https://nar-serve.numtide.com/nix/store/rkv4yh7pym941bhj0849zqdkg2546bdv-installer-script/install \
      | sh --tarball-url-prefix https://nar-serve.numtide.com/nix/store

Or with cachix, strip the /nix/store and derivation name and then:

    curl -sfL https://mycache.cachix.org/serve/rkv4yh7pym941bhj0849zqdkg2546bdv/install \
      | sh --tarball-url-prefix https://mycache.cachix.org/serve

Fixes #4047

This test no longer works on Hydra because import-from-derivation is
no longer allowed.

Until now, it was not possible to substitute missing paths from e.g.
`https://cache.nixos.org` on a remote server when building on it using
the new `ssh-ng` protocol.

This is because every store implementation except legacy `ssh://`
ignores the substitution flag passed to `Store::queryValidPaths` while
the `legacy-ssh-store` substitutes the remote store using
`cmdQueryValidPaths` when the remote store is opened with `nix-store
--serve`.

This patch slightly modifies the daemon protocol to allow passing an
integer value suggesting whether to substitute missing paths during
`wopQueryValidPaths`. To implement this on the daemon-side, the
substitution logic from `nix-store --serve` has been moved into a
protected method named `Store::substitutePaths` which gets currently
called from `LocalStore::queryValidPaths` and `Store::queryValidPaths`
if `maybeSubstitute` is `true`.

Fixes #2770

Fixes #4175

The move from release.nix to flake.nix appears to have lost some
changes from #3628 / 1c56f18a, leaving
create-darwin-volume.sh out of the release tarball.

Under the assumption that this was just an accident/byproduct of when
flake.nix split off and not intentional, I am restoring those edits.

checks should be relatively fast, but buildStatic depends on a lot of
stuff that isn't in the binary cache (e.g. musl builds of Git and
Mercurial that we probably don't need since we don't link against
them...).

Saves ~7s in the linking phase

They're still enabled in regular builds though.

Fix #4042

According to https://github.com/kristapsdz/lowdown/commit/8aef9e9290de22a10c14ae138257bc1c7fa8ba1f, we shouldn't need to use a fork anymore so we can switch back to upstream