child_process: fix deoptimizing use of arguments

Removed or fixed use of arguments in execFile(),
normalizeExecArgs(), and normalizeSpawnArguments().

Refs: https://github.com/nodejs/node/issues/10323
Refs: https://bugs.chromium.org/p/v8/issues/detail?id=6010
PR-URL: https://github.com/nodejs/node/pull/11535


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>