Eventually delete the CA paths lock files

Mark the lockfiles as having to eventually be deleted so that they don’t
stay laying around in the store at the end of the build

Fix #4936

src/libstore/build/local-derivation-goal.cc

@@ -2481,6 +2481,7 @@ void LocalDerivationGoal::registerOutputs()
            floating CA derivations and hash-mismatching fixed-output
            derivations. */
         PathLocks dynamicOutputLock;
+        dynamicOutputLock.setDeletion(true);
         auto optFixedPath = output.path(worker.store, drv->name, outputName);
         if (!optFixedPath ||
             worker.store.printStorePath(*optFixedPath) != finalDestPath)