github-actions: add multiarch support

Author: itslychee

.github/workflows/test.yml

@@ -1,3 +1,4 @@
+---
 name: "Test"
 on:
   pull_request:
@@ -98,11 +99,17 @@ jobs:
           sudo rm -rf /opt/hostedtoolcache/CodeQL
           sudo docker image prune --all --force
       - uses: actions/checkout@v4
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+        with:
+          platforms: arm64
       - uses: cachix/install-nix-action@v31
         with:
           nix_path: nixpkgs=channel:nixos-unstable
           enable_kvm: true
-          extra_nix_config: "system-features = nixos-test benchmark big-parallel kvm"
+          extra_nix_config: |
+            system-features = nixos-test benchmark big-parallel kvm
+            extra-platforms = aarch64-linux i686-linux
       - uses: cachix/cachix-action@v16
         with:
           name: wires