Hadrian does not track package db cache
While @nh2 and @bgamari were discussing a problem, they ended up realizing that deleting
_build/stage0/lib/package.conf.d/package.cache and issuing a hadrian command to rebuild it and resume the build where it was previously failing results in:
ghc: there is no package.cache in _build/stage0/lib/package.conf.d even though package database is not empty
It's probably safe to assume that Hadrian does not track the package db cache in any way (not even using
traceWrite or anything like that). It'd be nice to teach Hadrian enough about those caches for it to be able to regenerate them when needed.