fix nix flake check on macOS

.github/workflows/test-flakes.yml

@@ -16,7 +16,6 @@ jobs:
           fetch-depth: 0
     - uses: cachix/install-nix-action@v14
       with:
-        install_url: https://github.com/numtide/nix-flakes-installer/releases/download/nix-2.4pre20201221_9fab14a/install
         extra_nix_config: |
           experimental-features = nix-command flakes
           system-features = nixos-test benchmark big-parallel kvm
@@ -27,5 +26,5 @@ jobs:
         signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'
     - name: List flake structure
       run: nix flake show
-    - name: Run unit tests (flake)
-      run: nix build --no-link .#unit-tests -L
+    - name: Run flake check (flake)
+      run: nix flake check -L

default.nix

@@ -11,7 +11,6 @@ in rec {
     Also see https://github.com/Mic92/sops-nix/issues/98
   '' pkgs.callPackage ./pkgs/sops-pgp-hook { };
   sops-import-keys-hook = pkgs.callPackage ./pkgs/sops-import-keys-hook { };
-  inherit sops-install-secrets;
 
   # backwards compatibility
   inherit (pkgs) ssh-to-pgp;
@@ -26,8 +25,9 @@ in rec {
       install -D sops-pgp-hook.test $out/bin/sops-pgp-hook.test
     '';
   };
-
   unit-tests = pkgs.callPackage ./unit-tests.nix {};
+} // (pkgs.lib.optionalAttrs pkgs.stdenv.isLinux {
+  inherit sops-install-secrets;
 
   lint = sops-install-secrets.overrideAttrs (old: {
     name = "golangci-lint";
@@ -54,4 +54,4 @@ in rec {
     '';
     fixupPhase = ":";
   });
-}
+})