Make the flake options work when using the daemon

When setting flake-local options (with the `nixConfig` field), forward
these options to the daemon in case we’re using one.

This is necessary in particular for options like `binary-caches` or
`post-build-hook` to make sense.

Fix <343239fc8a (r44356843)>

src/libstore/remote-store.cc

@@ -290,6 +290,10 @@ ConnectionHandle RemoteStore::getConnection()
     return ConnectionHandle(connections->get());
 }
 
+void RemoteStore::setOptions()
+{
+    setOptions(*(getConnection().handle));
+}
 
 bool RemoteStore::isValidPathUncached(const StorePath & path)
 {