ci/pkgtest: make nixos-unstable into a x86+arm matrix

Other pkgtest jobs can't do this, as they're designed for LXC
and we don't have an arm+LXC runner.

diff --git a/ci/pkgtest.yaml b/ci/pkgtest.yaml
index d2eb61265c43b9465d10d8e3cfd57befe033e9a1..87df49f9a7229ab0e0c94a6e02333bee72b7f0ea 100644 (file)
--- a/ci/pkgtest.yaml
+++ b/ci/pkgtest.yaml
@@ -143,12 +143,14 @@ ubuntu-21.10:pkgbuild:
 nixos-unstable:pkgbuild:
   <<: *pkgbuild
   # We do NOT use LXC, for now at least.
+  parallel:
+    matrix:
+      - PLATFORM: [ amd64, arm64 ]
   tags:
     - docker
     - linux
-    - amd64
-  # TODO: untag after resolving problems around https://github.com/NixOS/nix/issues/5776
-  image: nixos/nix:2.3.12
+    - ${PLATFORM}
+  image: nixos/nix
 
   variables:
     #NIX_PATH: nixpkgs=https://github.com/nixos/nixpkgs/archive/nixos-unstable.tar.gz