ghc963 with debugging build flags for MacOS

[chessai]

For @jwiegley to test.

[jwiegley]

Thanks, I was able to build and run with this. It still dumped core, but now I have a build that Ben Gamari can help me with.

[imalsogreg]

Awesome that the shell is working!

If I am interpreting nix flake show correctly for this branch, our nixpkgs input follows haskellNix/nixpkgs, which uses nixpkgs-unstable, which (for our current pin of haskell-nix) is github:NixOS/nixpkgs/e12483116b3b51a185a33a272bf351e357ba9a99. We may want to explicitly name the nixpkgs revision in our flake file like we currently do on master, rather than keeping nixpkgs.follows = "haskellNix/nixpkgs" in our flake.nix, since the former is easier to eyeball compare between repositories. I mean:

--- a/flake.nix
+++ b/flake.nix
@@ -2,7 +2,7 @@
   description = "Chainweb";

   inputs = {
-    nixpkgs.follows = "haskellNix/nixpkgs"; 
+    nixpkgs.url = "github:NixOS/nixpkgs?rev=e12483116b3b51a185a33a272bf351e357ba9a99";

I haven't actually tested this yet, so buyer beware!