fix: use ephemeral runner for aarch64 builds

Author: jfroche

.github/workflows/nix-build.yml

@@ -35,8 +35,11 @@ jobs:
     steps:
       - name: Checkout Repo
         uses: actions/checkout@v4
-      - name: Build Nix Package
-        uses: ./.github/actions/nix-install-self-hosted
+      - name: Install nix
+        uses: ./.github/actions/nix-install-ephemeral
+        env:
+          DEV_AWS_ROLE: ${{ secrets.DEV_AWS_ROLE }}
+          NIX_SIGN_SECRET_KEY: ${{ secrets.NIX_SIGN_SECRET_KEY }}
       - name: nix build
         shell: bash
         run: nix build --accept-flake-config -L .#${{ matrix.attr }}