child_process: support execArgv in spawn()

The execArgv option passed to spawn() was being silently ignored.
This commit adds proper handling of execArgv in normalizeSpawnArguments(),
prepending the execArgv values to the args array before argv0/file.

Fixes: #65725
PR-URL: #65726

Author: dajiaohuang

doc/api/child_process.md

@@ -695,6 +695,7 @@ changes:
   * `env` {Object} Environment key-value pairs. **Default:** `process.env`.
   * `argv0` {string} Explicitly set the value of `argv[0]` sent to the child
     process. This will be set to `command` if not specified.
+  * `execArgv` {string\[]} List of string arguments passed to the executable.
   * `stdio` {Array|string} Child's stdio configuration (see
     [`options.stdio`][`stdio`]).
   * `detached` {boolean} Prepare child process to run independently of

lib/child_process.js

@@ -691,6 +691,13 @@ function normalizeSpawnArguments(file, args, options) {
     }
   }
 
+  // Handle execArgv - prepend to args if provided
+  if (options.execArgv != null) {
+    validateArray(options.execArgv, 'options.execArgv');
+    validateArgumentsNullCheck(options.execArgv, 'options.execArgv');
+    args = [...options.execArgv, ...args];
+  }
+
   if (typeof options.argv0 === 'string') {
     ArrayPrototypeUnshift(args, options.argv0);
   } else {
@@ -788,6 +795,7 @@ function abortChildProcess(child, killSignal, reason) {
  *   cwd?: string | URL;
  *   env?: Record<string, string>;
  *   argv0?: string;
+ *   execArgv?: string[];
  *   stdio?: Array | string;
  *   detached?: boolean;
  *   uid?: number;