Fixed emscripten breaks on NixOS due to lack of FHS

flake.nix

@@ -16,6 +16,15 @@
       };
     in
       pkgs.mkShell {
+        # Ref: https://github.com/NixOS/nixpkgs/issues/139943
+        # EM_CONFIG = pkgs.writeText ".emscripten" ''
+        #   EMSCRIPTEN_ROOT = '${pkgs.emscripten}/share/emscripten'
+        #   LLVM_ROOT = '${pkgs.emscripten.llvmEnv}/bin'
+        #   BINARYEN_ROOT = '${pkgs.binaryen}'
+        #   NODE_JS = '${pkgs.nodejs_24}/bin/node'
+        #   CACHE = '${toString ./.cache}'
+        # '';
+
         packages = with pkgs; [
           openssl
           gnumake
@@ -25,6 +34,10 @@
         shell = "${pkgs.bash}/bin/bash";
 
         shellHook = ''
+          export EM_CACHE=$PWD/.emscripten_cache
+          cp -r ${pkgs.emscripten}/share/emscripten/cache $EM_CACHE
+          chmod u+rwX -R $EM_CACHE
+
           function makejs { make -f Makefile.js $@; }
         '';
       };