Add Nix flake

Using it for CI is much more elegant than the current Ubuntu PPA
dumpster fire plus we can easily run it locally.

.github/workflows/ci.yml

@@ -2,19 +2,10 @@ name: Continuous Integration
 on: [push, pull_request]
 jobs:
   build:
-    strategy:
-      matrix:
-        cxx: [g++, clang++]
     runs-on: ubuntu-latest
-    env:
-      CXX: ${{ matrix.cxx }}
     steps:
-    - uses: actions/checkout@v3
-    - name: Install dependencies
-      run: sudo apt install -y libseccomp-dev && sudo add-apt-repository ppa:ubuntu-toolchain-r/test && sudo apt-get update && sudo apt-get -y install gcc-14 && sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-14 30
-    - name: Configure the project
-      run: cmake -B build -DCMAKE_BUILD_TYPE=Debug
-    - name: Build the project
-      run: cmake --build build
-    - name: Run tests
-      run: tests/run-tests.sh
+    - uses: actions/checkout@v4
+    - uses: cachix/install-nix-action@v27
+      with:
+        nix_path: nixpkgs=channel:nixos-unstable
+    - run: nix flake check --print-build-logs

CMakeLists.txt

@@ -1,5 +1,5 @@
 cmake_minimum_required(VERSION 3.21)
-project(copycat)
+project(copycat VERSION 0.1)
 
 set(LIB_TARGET "${PROJECT_NAME}")
 set(BIN_TARGET "${PROJECT_NAME}-bin")

flake.nix

@@ -0,0 +1,32 @@
+{
+	description = "A library for intercepting system calls";
+	inputs = {
+		quartz.url = "github:vimpostor/quartz";
+	};
+
+	outputs = { self, quartz }: quartz.lib.eachSystem (system:
+		let
+			pkgs = quartz.inputs.nixpkgs.legacyPackages.${system};
+			stdenvs = [ { name = "gcc"; pkg = pkgs.gcc14Stdenv; } { name = "clang"; pkg = pkgs.llvmPackages_18.stdenv; } ];
+			defaultStdenv = (builtins.head stdenvs).name;
+			makeStdenvPkg = env: env.mkDerivation {
+				pname = "copycat";
+				version = quartz.lib.cmakeProjectVersion ./CMakeLists.txt;
+
+				src = ./.;
+
+				nativeBuildInputs = with pkgs; [
+					cmake
+					libseccomp
+				];
+			};
+		in {
+			packages = {
+				default = self.outputs.packages.${system}.${defaultStdenv};
+			} // builtins.listToAttrs (map (x: { name = x.name; value = makeStdenvPkg x.pkg; }) stdenvs);
+			checks = {
+				format = pkgs.runCommand "format" { src = ./.; nativeBuildInputs = [ pkgs.clang-tools pkgs.git ]; } "mkdir $out && cd $src && find . -type f -path './*\\.[hc]pp' -exec clang-format -style=file --dry-run --Werror {} \\;";
+			} // builtins.listToAttrs (map (x: { name = "tests-" + x.name; value = (makeStdenvPkg x.pkg); }) stdenvs);
+		}
+	);
+}