pr-8130

synopsis: Split up `Distribution.Simple.Setup`
packages: Cabal
prs: #8130

description: {

The external interface of 'Distribution.Simple.Setup' has been kept the same, but internally it has been broken up into smaller modules.
This improves build times in two ways:
1. GHC is superlinear in the size of files, meaning that splitting up a large file can reduce overall compile times.
2. Breaking up the module allows dependent modules to refine their imports to just the parts they require, allowing them to start buildling quicker
when GHC is run in parrallel make mode ('--ghc-options -j').

}