codegen: fix padding calculation for error unions when lowering

* do not track `rdi` register before `call` inst, but instead freeze
  it from further use, until `call` has been realised
* pass more error union tests
12cdb36c5bJakub Konka committed on 2/28/2022, 10:20:05 PMparent05431d7
3 files changedLine totals unavailable