Hadrian: correct deps for ghc builder.
Previously, when needing ghc as a builder, the ghcDeps (Files the GHC binary depends on) for the current stage were needed. This is incorrect as the previous stage's ghc is used for building. This commit fixes the issue, needing the previous stage's ghcDeps.
This fixes 25,425 missing need lint errors, and 25,432 late need lint errors.