Add firefox only on non-darwin systems' flake.nix

flake.nix

@@ -17,7 +17,7 @@
         pkgs = import nixpkgs { inherit system overlays; };
         rust = pkgs.rust-bin.fromRustupToolchainFile ./rust-toolchain.toml;
         inputs = [
-	  rust
+          rust
           pkgs.rust-analyzer
           pkgs.openssl
           pkgs.zlib
@@ -27,12 +27,15 @@
           pkgs.wasm-pack
           pkgs.wasm-bindgen-cli
           pkgs.binaryen
-	  pkgs.clang
+          pkgs.clang
           pkgs.corepack_20
           pkgs.nodejs_20
+        ] ++ pkgs.lib.optionals (!pkgs.stdenv.isDarwin) [
+          # Add firefox deps only on non-darwin.
+          # darwin is listed in badPlatforms in pkgs.firefox's meta.
           pkgs.firefox
           pkgs.geckodriver
-	];
+        ];
       in
       {
         defaultPackage = pkgs.rustPlatform.buildRustPackage {
@@ -47,14 +50,14 @@
 
 
         devShell = pkgs.mkShell {
-	  packages = inputs;
+          packages = inputs;
           shellHook = ''
-	    export LIBCLANG_PATH=${pkgs.libclang.lib}/lib/
+            export LIBCLANG_PATH=${pkgs.libclang.lib}/lib/
             export LD_LIBRARY_PATH=${pkgs.openssl}/lib:$LD_LIBRARY_PATH
             export CC_wasm32_unknown_unknown=${pkgs.llvmPackages_14.clang-unwrapped}/bin/clang-14
             export CFLAGS_wasm32_unknown_unknown="-I ${pkgs.llvmPackages_14.libclang.lib}/lib/clang/14.0.6/include/"
           '';
-	};
+        };
       }
     );
 }