nix: add shared haskell package set

haskell.nix

@@ -2,7 +2,7 @@
 # to our Haskell package extensions from other overlays, bypassing the
 # rest of our overlay.  This was necessary for rather obscure reasons.
 
-{ pkgs, lib, wrapped ? true }:
+{ pkgs, lib, wrapped ? true, shared ? false }:
 
 let
   stdenv = pkgs.stdenv;
@@ -57,7 +57,8 @@ in self-hs: super-hs:
       configureFlags = attrs.configureFlags ++ [
           "--ghc-option=-O2"
       ] ++
-      (if stdenv.isDarwin then [] else [
+      (if stdenv.isDarwin then [] else
+        if shared then [] else [
           "--enable-executable-static"
           "--extra-lib-dirs=${pkgs.gmp.override { withStatic = true; }}/lib"
           "--extra-lib-dirs=${pkgs.glibc.static}/lib"

overlay.nix

@@ -21,6 +21,13 @@ in rec {
     );
   });
 
+  sharedHaskellPackages =
+    super.haskellPackages.override (old: {
+    overrides = lib.composeExtensions (old.overrides or (_: _: {})) (
+      import ./haskell.nix { inherit lib; pkgs = self; wrapped = false; shared = true; }
+    );
+  });
+
   solidityPackage = import ./nix/solidity-package.nix {
     inherit (self) pkgs;
   };