Add dbg_node_fs/dbg_node_utils declarations to shell_minimal.js

runtime_debug.js references dbg_node_fs and dbg_node_utils when
ENVIRONMENT_MAY_BE_NODE with PTHREADS or WASM_WORKERS, but these
variables were only declared in shell.js, not in shell_minimal.js.
This caused Closure compiler to fail with JSC_UNDEFINED_VARIABLE
for MINIMAL_RUNTIME builds with threading and --closure=1.

Add the declarations for both paths:
- PTHREADS: inside the existing if(ENVIRONMENT_IS_NODE) block that
  already imports fs
- WASM_WORKERS without PTHREADS: in a new conditional block

Author: Bartek Wrona

src/shell_minimal.js

@@ -107,6 +107,11 @@ if (ENVIRONMENT_IS_NODE) {
   var fs = {{{ makeNodeImport('node:fs', false) }}};
   defaultPrint = (...args) => fs.writeSync(1, args.join(' ') + '\n');
   defaultPrintErr = (...args) => fs.writeSync(2, args.join(' ') + '\n');
+#if (ASSERTIONS || RUNTIME_DEBUG || AUTODEBUG)
+  var utils = {{{ makeNodeImport('node:util', false) }}};
+  var dbg_node_fs = fs;
+  var dbg_node_utils = utils;
+#endif
 }
 var out = defaultPrint;
 var err = defaultPrintErr;
@@ -115,6 +120,16 @@ var out = (...args) => console.log(...args);
 var err = (...args) => console.error(...args);
 #endif
 
+#if !PTHREADS && WASM_WORKERS && ENVIRONMENT_MAY_BE_NODE && (ASSERTIONS || RUNTIME_DEBUG || AUTODEBUG)
+// Initialize dbg() node module references for WASM_WORKERS without PTHREADS.
+// (With PTHREADS these are set in the print setup block above.)
+var dbg_node_fs, dbg_node_utils;
+if (ENVIRONMENT_IS_NODE) {
+  dbg_node_fs = {{{ makeNodeImport('node:fs', false) }}};
+  dbg_node_utils = {{{ makeNodeImport('node:util', false) }}};
+}
+#endif
+
 // Override this function in a --pre-js file to get a signal for when
 // compilation is ready. In that callback, call the function run() to start
 // the program.