tools: fix c-ares updater script for Node.js 18

[richardlau]

GitHub Actions is by default running the tools updater workflow with Node.js 18. Avoid use of import.meta.dirname, which wasn't backported to Node.js 18.

Refs: #55445

---

Example error, https://github.com/nodejs/node/actions/runs/11647004207/job/32431749696

node:internal/errors:496
    ErrorCaptureStackTrace(err);
    ^

TypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type string. Received undefined
    at new NodeError (node:internal/errors:405:5)
    at validateString (node:internal/validators:162:11)
    at join (node:path:1171:7)
    at file:///home/runner/work/node/node/tools/dep_updaters/update-c-ares.mjs:5:17
    at ModuleJob.run (node:internal/modules/esm/module_job:195:25)
    at async ModuleLoader.import (node:internal/modules/esm/loader:337:24)
    at async loadESM (node:internal/process/esm_loader:34:7)
    at async handleMainPromise (node:internal/modules/run_main:106:12) {
  code: 'ERR_INVALID_ARG_TYPE'
}

Node.js v18.20.4

We could introduce the setup-node action into the workflow to pick a later Node.js version, but Node.js 18 is still in support and it's fairly trivial to workaround.

[nodejs-github-bot]

Review requested:

• @nodejs/security-wg