chore(tvix/nix_cli): build with tests

only run test_nix_store_add() when the feature integration_tests is
enabled.

Change-Id: I600f08ecaefe1ce77651ae07a58d7987107ab969
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6084
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>

tvix/nix_cli/default.nix

@@ -3,6 +3,5 @@
 depot.third_party.naersk.buildPackage {
   src = ./.;
   doDoc = false;
-  # Tests invoke nix-store binary
-  doCheck = false;
+  doCheck = true;
 }