Address space remapping means rom will no longer be at 0x0
Because the remapping means rom no longer starts at 0x0, this assert will break.
I thought about checking that _start == 0x40000000 but ultimately that did not seem like a good idea to me either. If you have any alternatives to suggest besides dropping the assert I'd be interested.
https://gitlab.raptorengineering.com/kestrel-collaboration/kestrel-litex/litex-boards/-/merge_requests/5 (and related)