add nix install to mac

Author: AndreyMlashkin

.github/workflows/run_tests_mac.yml

@@ -35,7 +35,9 @@ jobs:
             ${{ github.workspace }}/**
             !${{ github.workspace }}/
             !${{ github.workspace }}/**/.git/**
-      
+      - uses: DeterminateSystems/nix-installer-action@main
+      - uses: DeterminateSystems/magic-nix-cache-action@main
+      - uses: DeterminateSystems/flake-checker-action@main
       # nix is taken from the cloud-init template, no need to install it.
       - name: Build and run tests
         run: |