Merge changes I81552018,Ieb65c133 into main

* changes:
  releng: add releaseTests flake output, test script
  add aarch64-linux as a cross-build target

doc/manual/src/contributing/hacking.md

@@ -175,6 +175,7 @@ These are specified in `crossSystems` in `flake.nix`; feel free to submit change
 
 - `armv6l-linux`
 - `armv7l-linux`
+- `aarch64-linux`
 - `riscv64-linux`
 
 For example, to cross-compile Lix for `armv6l-linux` from another Linux, use the following:

flake.nix

@@ -90,6 +90,7 @@
         "armv6l-linux"
         "armv7l-linux"
         "riscv64-linux"
+        "aarch64-linux"
         # FIXME: still broken in 24.05: fails to build rustc(??) due to missing -lstdc++ dep
         # "x86_64-freebsd"
         # FIXME: broken dev shell due to python
@@ -328,6 +329,25 @@
         pkgs = nixpkgsFor.x86_64-linux.native;
       };
 
+      releaseTests = lib.foldl lib.recursiveUpdate { } [
+        (lib.genAttrs (linux64BitSystems ++ darwinSystems) (system: {
+          nativeBuild = self.packages.${system}.nix;
+        }))
+        (lib.genAttrs (linux64BitSystems) (system: {
+          staticBuild = self.packages.${system}.nix-static;
+        }))
+        {
+          x86_64-linux = {
+            # TODO add more cross/static release targets?
+            crossBuild.aarch64-linux = self.packages.x86_64-linux.nix-aarch64-linux;
+
+            # TODO wire up a nixos installer test with that lix and
+            # run it, once nixpkgs can actually do that (again). :/
+            # # nix build .#nixosTests.installer.{btrfsSimple,luksroot,lvm,simple,switchToFlake}
+          };
+        }
+      ];
+
       # NOTE *do not* add fresh derivations to checks, always add them to
       # hydraJobs first (so CI will pick them up) and only link them here
       checks = forAvailableSystems (

releng/release-tests.sh

@@ -0,0 +1,36 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+shopt -s inherit_errexit failglob
+
+nixpkgss=(
+    "$(nix eval --impure --raw --expr '(import ./flake.nix).inputs.nixpkgs.url')"
+    "github:NixOS/nixpkgs/nixos-unstable-small"
+)
+jobs=(
+    $(nix eval \
+        --json --apply '
+          let f = n: t:
+            if builtins.isAttrs t
+            then (if t.type or "" == "derivation"
+                  then [ n ]
+                  else builtins.concatMap (m: f "${n}.${m}" t.${m}) (builtins.attrNames t))
+            else [];
+          in f ".#.releaseTests"
+        ' \
+        '.#.releaseTests' \
+        | jq -r '.[]'
+    )
+)
+
+for override in "${nixpkgss}"
+do
+    (
+        set -x
+        nix build \
+            --log-format multiline \
+            --no-link \
+            --override-input nixpkgs "$override" \
+            "${jobs[@]}"
+    )
+done