Gradle cleanup

[Sineaggi]

I've been doing some development, and came across a few warnings during build.

These are, Project::task is now deprecated, avoiding Project::mkdir, project::delete and Project::getProjectDir as they cannot work under configuration-cache.

---

Progress

• Change must not contain extraneous whitespace
• Change must be properly reviewed (no review required)

Error

 ⚠️ OCA signatory status must be verified

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jextract.git pull/283/head:pull/283
$ git checkout pull/283

Update a local copy of the PR:
$ git checkout pull/283
$ git pull https://git.openjdk.org/jextract.git pull/283/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 283

View PR using the GUI difftool:
$ git pr show -t 283

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jextract/pull/283.diff

[bridgekeeper]

Hi @Sineaggi, welcome to this OpenJDK project and thanks for contributing!

We do not recognize you as Contributor and need to ensure you have signed the Oracle Contributor Agreement (OCA). If you have not signed the OCA, please follow the instructions. Please fill in your GitHub username in the "Username" field of the application. Once you have signed the OCA, please let us know by writing /signed in a comment in this pull request.

If you already are an OpenJDK Author, Committer or Reviewer, please click here to open a new issue so that we can record that fact. Please use "Add GitHub user Sineaggi" as summary for the issue.

If you are contributing this work on behalf of your employer and your employer has signed the OCA, please let us know by writing /covered in a comment in this pull request.

[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[Sineaggi]

/signed

[bridgekeeper]

Thank you! Please allow for up to two weeks to process your OCA, although it is usually done within one to two business days. Also, please note that pull requests that are pending an OCA check will not usually be evaluated, so your patience is appreciated!