As a developer, buildCSS should not generate files into src folder

• Type: Story
• Status: Ready for QA
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: None
• Fix Version/s: 7.0.X, 7.1.X, 7.2.X, Master
• Component/s: Dev Tools
• Labels: None
• Branch Version/s:
  7.2.x, 7.1.x, 7.0.x
• Backported to Branch:
  Committed
• Git Pull Request: https://github.com/brianchandotcom/liferay-portal/pull/85185

We must fix buildCSS to generate files outside of the source folders. This will ensure our incremental cache to work properly since our source folders are not touched.

This story will fix both our gradle plugin, maven plugin, and project templates.