Adds custom handling of the GHC.Prim module during copy

This used to be done in `ghc-cabal`. With the long term goal of getting rid of ghc-cabal eventually, it's functionality needs to end up in cabal.

While this is a custom hack, it is restricted to the GHC module only. A more generic solution would be to add `virtual-modules` I suppose. GHC does custom handling for `GHC.Prim`, and there is no support for `virtual-modules` in the package config file either as far as I can see. As such this seems to be the least invasive solution.

Cabal/Distribution/Simple/GHC.hs

@@ -1,4 +1,5 @@
 {-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE CPP #-}
 
@@ -1734,8 +1735,11 @@ installLib verbosity lbi targetDir dynlibTargetDir _builtDir _pkg lib clbi = do
     installOrdinary = install False
     installShared   = install True
 
+    gHC_PRIM = "GHC.Prim" :: ModuleName
+    -- We ignore any "GHC.Prim" module. Which doesn't physically exist. It is part of
+    -- the @base@ package, and containes wired-in primitives.
     copyModuleFiles ext =
-      findModuleFiles [builtDir] [ext] (allLibModules lib clbi)
+      findModuleFiles [builtDir] [ext] (filter (/= gHC_PRIM) $ allLibModules lib clbi)
       >>= installOrdinaryFiles verbosity targetDir
 
     compiler_id = compilerId (compiler lbi)