Draft: Build on macOS

This patch allows stechec2 to build and run on macOS systems. It is only meant for local development and should not be used on a large scale.

The following problems were preventing stechec2 from running on macOS, that are now fixed:

• Absence of pthread_nt
  • As the name indicates, stechec2 relies on the function pthread_timedjoin_np, where np stands for non portable, it is only available on Linux(?) systems
  • A replacement has been added inside np.cc. It is very barebones and not optimized, but it works.
• .so and .dylib extensions
  • For some obscure reasons, shared libraries on macOS do not use .so but .dylib as the file extension
  • The functionality is the exact same, but one part of the code explicitely requested libc.so.6 when libc works just fine, it will determine the correct extension itself
  • Libraries built by stechec also contain the .dylib extension. As long as it is correctly written in YAML files, it makes no difference
  • Champion files are still coded to export as .so files. This is not an issue and they work fine too
• Missing librt
  • The library rt cannot be found on non Linux systems.
  • I haven't found any place where this is explicitely used, and it seems built into libc anyway, so I made it optional
• tictactoe not compiling with clang
  • I didn't get g++ to work, but clang++ worked. tictactoe was missing an import which raised a warning with g++, but clang++ considered it to be an error. The import was fixed
• gdb hasn't been ported to the ARM architecture
  • lldb works as an alternative, using the --debug-cmd flag

TODO

• Compiling champions doesn't work without including -undefined dynamic_lookup to the linking flags. I am not sure where or how to add this
• Documentation
• Testing on Linux
• Rust support

Notes for compiling

I got this to compile on my mac by modifying the flake and then using nix develop. I had to add these libraries for it to compile:

diff --git a/flake.nix b/flake.nix
index 420311f..9e2a819 100644
--- a/flake.nix
+++ b/flake.nix
@@ -36,7 +36,7 @@
           };

           devShell = pkgs.mkShell {
-            buildInputs = lib.attrValues self.packages.${system};
+            buildInputs = (lib.attrValues self.packages.${system}) ++ (with pkgs; [pkg-config cppzmq zeromq gflags ncurses lldb]);
           };
         }
       );