Bump dev cabal to 3.2 and use multiple subdirs feature

- The haskell.nix cabal now works, so that's nice.
- We can use the nice multiple-subdirs feature in cabal.project to cut
out a lot of repetition.

Note we get annoying warnings about extraneous version ranges due to
haskell/cabal#5119.

Author: michaelpj

nix/dev.nix

@@ -3,7 +3,7 @@ pkgs.recurseIntoAttrs (rec {
   # Packages which are useful during development, but we don't depend upon directly to build our stuff
   packages = pkgs.recurseIntoAttrs {
     # See comment on the definition about it not working
-    #cabal-install = haskell.extraPackages.cabal-install.components.exes.cabal;
+    cabal-install = haskell.extraPackages.cabal-install.components.exes.cabal;
     stylish-haskell = haskell.extraPackages.stylish-haskell.components.exes.stylish-haskell;
     hlint = haskell.extraPackages.hlint.components.exes.hlint;
     haskell-language-server = haskell.extraPackages.haskell-language-server.components.exes.haskell-language-server;

nix/haskell-extra.nix

@@ -6,15 +6,12 @@
 ############################################################################
 { pkgs, index-state, checkMaterialization }:
 {
-  # FIXME: this cabal can't be used for development purposes until
-  # https://github.com/input-output-hk/haskell.nix/issues/422 is fixed
-  # Also need to pick a version that builds properly
   cabal-install = pkgs.haskell-nix.hackage-package {
     name = "cabal-install";
-    version = "3.0.0.0";
+    version = "3.2.0.0";
     inherit index-state checkMaterialization;
     # Invalidate and update if you change the version or index-state
-    plan-sha256 = "08zkccwygm4g83chyiwbskkjfclm22vmhbx2s2rh0lvjkclqy6qc";
+    plan-sha256 = "1pah0hdljyppj51dwa0s8yjmi9dv75xqsk6fghlsz7a3r0dchcss";
   };
   stylish-haskell = pkgs.haskell-nix.hackage-package {
     name = "stylish-haskell";