nix: initial tooling

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: Ibc12bc627f65a4b1d3430bdf8b86db256a6a6964

.envrc

@@ -0,0 +1 @@
+use flake

flake.lock

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+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1763835633,
+        "narHash": "sha256-HzxeGVID5MChuCPESuC0dlQL1/scDKu+MmzoVBJxulM=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "050e09e091117c3d7328c7b2b7b577492c43c134",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

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+{
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs?ref=nixos-unstable";
+
+  outputs = {
+    self,
+    nixpkgs,
+    ...
+  }: let
+    systems = ["x86_64-linux" "aarch64-linux"];
+    forEachSystem = nixpkgs.lib.genAttrs systems;
+    pkgsForEach = nixpkgs.legacyPackages;
+  in {
+    packages = forEachSystem (system: {
+      sin = pkgsForEach.${system}.callPackage ./nix/package.nix {};
+      default = self.packages.${system}.sin;
+    });
+
+    devShells = forEachSystem (system: {
+      default = pkgsForEach.${system}.mkShell {
+        inputsFrom = [self.packages.${system}.default];
+      };
+    });
+  };
+}

nix/package.nix

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+{
+  lib,
+  stdenv,
+  systemdSupport ? lib.meta.availableOn stdenv.hostPlatform systemd,
+  systemd,
+}:
+stdenv.mkDerivation {
+  pname = "sin";
+  version = "0.1.0";
+
+  src = let
+    fs = lib.fileset;
+    s = ../.;
+  in
+    fs.toSource {
+      root = s;
+      fileset = fs.unions [
+        (s + /Makefile)
+        (s + /main.c)
+      ];
+    };
+
+  strictDeps = true;
+  buildInputs = lib.optionals systemdSupport [systemd];
+
+  installPhase = ''
+    runHook preInstall
+
+    mkdir -p $out/bin
+    install -Dm755 sin $out/bin/sin
+
+    runHook postInstall
+  '';
+
+  meta = {
+    description = "Keep system idle inhibited while named processes run";
+    license = lib.licenses.mit;
+    maintainers = [lib.maintainers.NotAShelf];
+    platforms = lib.platforms.linux;
+  };
+}