Grails 5.0.2 projects are never up to date as findMainClass does not declare outputs

[andrewcanby-finocomp]

Steps to Reproduce

1. Create a vanilla Grails 5.0.2 project
   • NOTE: MUST fix the gson-views dependency to 2.1.1
2. Build the project

   ./gradlew build --info
   # snip
   BUILD SUCCESSFUL in 1m 56s
   11 actionable tasks: 10 executed, 1 up-to-date

3. Rebuild the project without making any changes

    ./gradlew build --info
    # snip
    > Task :findMainClass
    Caching disabled for task ':findMainClass' because:
      Build cache is disabled
    Task ':findMainClass' is not up-to-date because:
      Task has not declared any outputs despite executing actions.
    :findMainClass (Thread[Execution worker for ':',5,main]) completed. Took 0.001 secs.
    # snip
    BUILD SUCCESSFUL in 42s
    10 actionable tasks: 1 executed, 9 up-to-date

Expected Behaviour

Gradle up-to-date checks should identify that there have been no changes and the project should not need rebuilding

Actual Behaviour

Gradle is identifying that :findMainClass is never up to date, and always rebuilds it and it's dependents:

> Task :findMainClass
Caching disabled for task ':findMainClass' because:
  Build cache is disabled
Task ':findMainClass' is not up-to-date because:
  Task has not declared any outputs despite executing actions.
:findMainClass (Thread[Execution worker for ':',5,main]) completed. Took 0.001 secs.

Environment Information

• Operating System: Mac OS 11
• Grails Version: 5.0.2
• JDK Version: 11.0.8
• Container Version (If Applicable): N/A

Example Application

• Use any vanilla Grails 5.0.2 application