Handle building of XAP keymaps on master/develop

[zvecr]

Description

When the CI Build Major Branch workflow runs on master/develop, it attempts to find xap keymaps. As the feature is still on its own branch, zero keymaps are found. These targets are then passed to qmk mass-compile. In the case of zero keymaps, qmk mass-compile is then given zero additional target arguments and in turn builds everything.

This additional build should be avoided as it is both extremely slow, and completely unnecessary due to it already building in batches.

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout (addition or update)
• Documentation

Issues Fixed or Closed by This PR

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).