Speed up build by making assumptions

[koppor]

We generate *.mv and citation-style-catalog.json.

Gradle runs these tasks even if the input directory does not change.

The input directory do not change that often; ignoring these speeds up the build significantly.

Assumptions:

• GitHub CI starts on blank build directory
• Developers seldomly work on parts of jabref requiring fresh abbreviation lists and new/other citation styles
• If developers work in the area of mv files, they will refresh these files on their own.

Mandatory checks

• I own the copyright of the code submitted and I license it under the MIT license
• [/] Change in CHANGELOG.md described in a way that is understandable for the average user (if change is visible to the user)
• [/] Tests created for changes (if applicable)
• [/] Manually tested changed features in running JabRef (always required)
• [/] Screenshots added in PR description (if change is visible to the user)
• [/] Checked developer's documentation: Is the information available and up to date? If not, I outlined it in this pull request.
• [/] Checked documentation: Is the information available and up to date? If not, I created an issue at https://github.com/JabRef/user-documentation/issues or, even better, I submitted a pull request to the documentation repository.

[trag-bot]

@trag-bot didn't find any issues in the code! ✅✨