Caching is always disabled when using AWS CodeBuild

I’m trying to use an EFS volume on CodeBuild to cache compiled classes between builds, using Gradle 6.

From looking at the debug log output below, it seems that Gradle is disabling caching for two reasons:

  1. Something about forking… does forking disable caching?
  2. It says the output property has been removed. What does that mean? This is showing the wrong path (/codebuild/output/src133641298/src/git-codecommit.us-east-1.amazonaws.com/v1/repos/HamsterBall/out/production/ProscAmazonSimpleDB), the correct path (/SharedVolume/MirrorSyncBuild/out/production/ProscAmazonSimpleDB) is just a few lines lower in the log, so I know I’m setting it correctly.
2022/09/22 21:59:50 null null
INFO: 2022-09-22T22:00:57.955+0000 [INFO] [org.gradle.internal.execution.steps.ResolveCachingStateStep] Caching disabled for task ':ProscAmazonSimpleDB:compileJava' because:
  'Forking compiler via ForkOptions.executable' satisfied
2022-09-22T22:00:57.955+0000 [DEBUG] [org.gradle.internal.operations.DefaultBuildOperationExecutor] Completing Build operation 'Snapshot task inputs for :ProscAmazonSimpleDB:compileJava'
2022-09-22T22:00:57.955+0000 [DEBUG] [org.gradle.internal.operations.DefaultBuildOperationExecutor] Build operation 'Snapshot task inputs for :ProscAmazonSimpleDB:compileJava' completed
2022-09-22T22:00:57.956+0000 [DEBUG] [org.gradle.internal.execution.steps.SkipUpToDateStep] Determining if task ':ProscAmazonSimpleDB:compileJava' is up-to-date
2022-09-22T22:00:57.956+0000 [INFO] [org.gradle.internal.execution.steps.SkipUpToDateStep] Task ':ProscAmazonSimpleDB:compileJava' is not up-to-date because:
  Output property 'destinationDirectory' file /codebuild/output/src133641298/src/git-codecommit.us-east-1.amazonaws.com/v1/repos/HamsterBall/out/production/ProscAmazonSimpleDB has been removed.
  Output property 'destinationDirectory' file /codebuild/output/src133641298/src/git-codecommit.us-east-1.amazonaws.com/v1/repos/HamsterBall/out/production/ProscAmazonSimpleDB/com has been removed.
  Output property 'destinationDirectory' file /codebuild/output/src133641298/src/git-codecommit.us-east-1.amazonaws.com/v1/repos/HamsterBall/out/production/ProscAmazonSimpleDB/com/prosc has been removed.
2022-09-22T22:00:57.956+0000 [DEBUG] [org.gradle.internal.execution.steps.CreateOutputsStep] Ensuring directory exists for property destinationDirectory at /SharedVolume/MirrorSyncBuild/out/production/ProscAmazonSimpleDB
2022-09-22T22:00:57.959+0000 [DEBUG] [org.gradle.internal.execution.steps.CreateOutputsStep] Ensuring directory exists for property options.generatedSourceOutputDirectory at /SharedVolume/MirrorSyncBuild/out/gradle/ProscAmazonSimpleDB/generated/sources/annotationProcessor/java/main
2022-09-22T22:00:57.962+0000 [DEBUG] [org.gradle.internal.execution.steps.CreateOutputsStep] Ensuring directory exists for property options.headerOutputDirectory at /SharedVolume/MirrorSyncBuild/out/gradle/ProscAmazonSimpleDB/generated/sources/headers/java/main
2022-09-22T22:00:57.976+0000 [INFO] [org.gradle.internal.execution.steps.ResolveInputChangesStep] The input changes require a full rebuild for incremental task ':ProscAmazonSimpleDB:compileJava'.