We're now past C++ bootstrap.

Layers in the 1xx series are in bare SubX, without any syntax sugar. They are
intended to be used by the phases of the self-hosted translator to replicate
the functionality of the C++ bootstrap:
  apps/hex.subx
  apps/survey.subx
  apps/pack.subx
  apps/dquotes.subx
  apps/assort.subx
  apps/tests.subx