Nix support (#1020)

Very hacky
Will be maintained by @NotNite

INSTALL.md

@@ -6,6 +6,7 @@ This repository supports:
 - [macOS](#unix)
 - [Windows Subsystem for Linux 2](#wsl-2)
 - [Docker](#docker) (any host OS)
+- [Nix](#nix)
 
 If you encounter any issues setting up the repo, please feel free to [reach out to us on Discord](https://discord.gg/urUm3VG).
 
@@ -77,3 +78,14 @@ docker run --rm -ti -v $(pwd):/papermario pm
 ```
 
 Then continue with [the instructions for Linux](#unix), but you can skip the install.sh!
+
+## Nix
+
+Install [Nix](https://nixos.org/download.html) and run `nix-shell`. You will need to set the `NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM` environment variable to `1` (required for cross compiling).
+
+```sh
+export NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM=1
+nix-shell
+```
+
+Like the instructions for Docker, continue with [the instructions for Linux](#unix), but you can skip the install.sh!

shell.nix

@@ -0,0 +1,77 @@
+{ pkgsNative ? import <nixpkgs> { }
+, pkgsCross ? import <nixpkgs> { crossSystem = { config = "mips-linux-gnu"; }; }
+}:
+
+let
+  mach-nix = import (builtins.fetchGit {
+    url = "https://github.com/DavHau/mach-nix";
+    ref = "master";
+    rev = "8d903072c7b5426d90bc42a008242c76590af916";
+  }) { };
+
+  mach-nix-python = mach-nix.mkPython {
+    requirements = ''
+      ${builtins.readFile ./requirements.txt}
+      ${builtins.readFile ./requirements_extra.txt}
+    '';
+  };
+
+  gcc-papermario = builtins.fetchurl {
+    url =
+      "https://github.com/pmret/gcc-papermario/releases/download/master/linux.tar.gz";
+    sha256 = "1156cf0d6a88a64c20e2a10fc9445d99cb9a38518f432b1669528dfa82ebb45f";
+  };
+
+  binutils-papermario = builtins.fetchurl {
+    url =
+      "https://github.com/pmret/binutils-papermario/releases/download/master/linux.tar.gz";
+    sha256 = "c3cd88db47ac41f78b557042c7e7ad47ac9c04cee6f0d1069a489c1c9e8c103c";
+  };
+
+  gcc-papermario-272 = builtins.fetchurl {
+    url =
+      "https://github.com/decompals/mips-gcc-2.7.2/releases/download/main/gcc-2.7.2-linux.tar.gz";
+    sha256 = "ff3e299c1d952c0a5cb39f7790a208d0c547cf93986eb5607f820c935cedc288";
+  };
+
+  binutils-papermario-272 = builtins.fetchurl {
+    url =
+      "https://github.com/decompals/mips-binutils-2.6/releases/download/main/binutils-2.6-linux.tar.gz";
+    sha256 = "405a7ddb29a0b2eb472b167e8f15472223df1eff3093a5ff31d6e545d3a6c670";
+  };
+
+  ido = builtins.fetchurl {
+    url =
+      "https://github.com/decompals/ido-static-recomp/releases/download/v0.2/ido-5.3-recomp-ubuntu-latest.tar.gz";
+    sha256 = "65b42b9673b6f439e45e5dafab1eca4fc006a68cda87bdb55681f027d9fb903c";
+  };
+in pkgsCross.mkShell {
+  nativeBuildInputs = (with pkgsNative; [
+    ninja
+    zlib
+    libyaml
+    patchelf
+    glibc
+    gcc
+    mach-nix-python
+  ]);
+  buildInputs = (with pkgsCross; [ gcc binutils ]);
+
+  # This is a very un-Nix-y way of doing things
+  shellHook = ''
+    tar zx -C tools/build/cc/gcc -f ${gcc-papermario}
+    tar zx -C tools/build/cc/gcc -f ${binutils-papermario}
+
+    tar zx -C tools/build/cc/gcc2.7.2 -f ${gcc-papermario-272}
+    tar zx -C tools/build/cc/gcc2.7.2 -f ${binutils-papermario-272}
+
+    tar zx -C tools/build/cc/ido5.3 -f ${ido}
+
+    for dir in $(find tools/build/cc -type d); do
+      for f in $(find $dir -type f); do
+        # Silence errors instead of thinking hard about this
+        ${pkgsNative.patchelf}/bin/patchelf --set-interpreter "${pkgsNative.glibc}/lib/ld-linux-x86-64.so.2" $f 2>/dev/null
+      done
+    done
+  '';
+}