fix fs.mkdir regression

[dylan-conway]

What does this PR do?

Fixes recursive: true throwing when the directory already exists

closes #16474

How did you verify your code works?

Added a regression test

[robobun]

^{Updated 4:10 PM PT - Jan 19th, 2025}

❌ @dylan-conway, your commit e0bec8a has 1 failures in #10114:

• test/js/web/fetch/fetch.test.ts - 1 failing on 🍎 13 aarch64

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🧪   try this PR locally:

bunx bun-pr 16497

[okineadev]

🧪   try this PR locally:

bunx bun-pr 16497

I tested this build, it fixed my issue which I wrote in #16474 (comment) 👍

[okineadev]

And another question, will you release a hotfix with this fix?

[Jarred-Sumner]

This will be in Bun v1.1.46 which releases today (once the tests are fixed)