Fix enableRelocatedStaticLibs.

[TravisWhitaker]

No description provided.

[hamishmack]

bors try

[iohk-bors]

try

Build failed:

• ci/hydra:Cardano:haskell-nix:required

[michaelpj]

Do these settings need some comments explaining why we need them?

[hamishmack]

I think this might be causing hydra to fail to build windows cross compiler due to Log limit exceeded error https://hydra.iohk.io/build/13649681

[TravisWhitaker]

I'd love to add an explanation here, but unfortunately I don't know one. As far as I can tell -fexternal-dynamic-refs is an undocumented GHC option, and I only know that it's necessary in addition to -fPIC to produce position independent code on X86_64 via experimentation.

The enableRelocatedStaticLibs option is definitely broken without this change, though.

[cdepillabout]

I'd love to add an explanation here, but unfortunately I don't know one.

We had this same conversation in Nixpkgs: NixOS/nixpkgs#162374 (comment)

[TravisWhitaker]

@hamishmack @michaelpj What's necessary to merge this? It's required to build working relocatable machine code on x86_64.

[hamishmack]

We need to find a fix for this https://hydra.iohk.io/build/13649664

[mklca]

This is a typo, surely? GhcLibHcOpts is the target of both assignments.

I've had success building a statically linked x86_64-unknown-linux-musl binary using projectCross.musl64 and ghc923 with this version.

[hamishmack]

Merged in #1569