nix: add support to build with GCC

Signed-off-by: Amneesh Singh <natto@weirdnatto.in>

nix/build.nix

@@ -0,0 +1,23 @@
+{ stdenv
+, meson
+, ninja
+, pkg-config
+, src ? "../."
+, libraries ? [ ]
+}:
+
+stdenv.mkDerivation {
+  name = "matar";
+  version = "0.1";
+  inherit src;
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+  ] ++ libraries;
+
+  enableParallelBuilding = true;
+}

nix/default.nix

@@ -0,0 +1,11 @@
+{ ... }: {
+  imports = [
+    ./matar.nix
+    ./matar-clang.nix
+  ];
+
+  perSystem = { self', pkgs, ... }: {
+    packages.default = self'.packages.matar-clang;
+    devShells.default = self'.devShells.matar-clang;
+  };
+}

nix/matar-clang.nix

@@ -0,0 +1,22 @@
+{ ... }: {
+  perSystem = { pkgs, src, ... }:
+    let
+      llvm = pkgs.llvmPackages_16;
+      stdenv = llvm.libcxxStdenv;
+
+      libraries = with pkgs; [
+        ((pkgs.fmt.override {
+          inherit stdenv;
+          enableShared = false;
+        }).overrideAttrs (oa: {
+          cmakeFlags = oa.cmakeFlags ++ [ "-DFMT_TEST=off" ];
+        })).dev
+
+        (catch2_3.override { inherit stdenv; }).out
+      ];
+    in
+    {
+      packages.matar-clang = pkgs.callPackage ./build.nix { inherit src libraries stdenv; };
+      devShells.matar-clang = pkgs.callPackage ./shell.nix { inherit libraries stdenv; };
+    };
+}

nix/matar.nix

@@ -0,0 +1,13 @@
+{ ... }: {
+  perSystem = { pkgs, src, ... }:
+    let
+      libraries = with pkgs; [
+        (pkgs.fmt.override { enableShared = false; }).dev
+        catch2_3.out
+      ];
+    in
+    {
+      packages.matar = pkgs.callPackage ./build.nix { inherit src libraries; };
+      devShells.matar = pkgs.callPackage ./shell.nix {inherit libraries;};
+    };
+}

nix/shell.nix

@@ -0,0 +1,19 @@
+{ stdenv
+, mkShell
+, meson
+, ninja
+, pkg-config
+, libraries ? [ ]
+}:
+
+mkShell.override { inherit stdenv; } {
+  name = "matar";
+
+  packages = [
+    meson
+    ninja
+    pkg-config
+  ] ++ libraries;
+
+  enableParallelBuilding = true;
+}