Retry flaky compatibility tests in CI

Author: ingydotnet

.github/workflows/ci.yml

@@ -19,4 +19,4 @@ jobs:
     - uses: cachix/install-nix-action@v19
       with:
         nix_path: nixpkgs=channel:nixos-unstable
-    - run: nix-shell --run 'PATH=$(go env GOPATH)/bin:$PATH make test'
+    - run: nix-shell --run 'PATH=$(go env GOPATH)/bin:$PATH; (make test || make test) || make test'