Cabal's recompilation avoidance not working correctly.

[hsyl20]

In #3 I've modified ghc-lib's source code but it ended building a bindist embedding the old version of ghc-lib...

I don't know how to reproduce this nor how to debug this for now, but it's bad.

[andreabedini]

Without any way to reproduce this I cannot confirm :-/ cabal should give enough information to figure out why it is not rebuilding something.

I remember there was an issue with GHC recompilation avoidance actually. Cabal would run GHC again but then GHC would think nothing has changed and skip recompiling. That must have been with GHC 9.4 though, I do not remember.

[hsyl20]

Actually it could also be a bug in Build.hs:

• we first build boot libraries
• then we build GHC assuming cabal will reuse the boot libraries we just built, but maybe it doesn't. Maybe it reuses the globally installed ones (they have the same version...).

We should somehow build and copy libraries and programs all at once, without installing them. Not sure if it is possible. Maybe we need some command like v1-copy to do this?