Fix dockerfile setup resources

[rorueda]

Use lazy evaluation of the layers' files to avoid triggering dependency resolution during configuration.

After upgrading to 4.3.1, I started getting the error below during configuration - the message is a bit misleading, but I think the stack points to the root cause.

An exception occurred applying plugin request [id: 'java-platform']
> Failed to apply plugin 'org.gradle.java-platform'.
   > Project#afterEvaluate(Action) on project ':bom' cannot be executed in the current context.

org.gradle.api.plugins.InvalidPluginException: An exception occurred applying plugin request [id: 'java-platform']
	...
	at org.gradle.api.internal.file.CompositeFileCollection.isEmpty(CompositeFileCollection.java:66)
	at io.micronaut.gradle.docker.MicronautDockerfile.setupResources(MicronautDockerfile.java:228)
	at io.micronaut.gradle.docker.MicronautDockerfile.setupInstructions(MicronautDockerfile.java:137)
	at io.micronaut.gradle.docker.MicronautDockerfile.setupTaskPostEvaluate(MicronautDockerfile.java:170)
	at io.micronaut.gradle.docker.MicronautDockerPlugin.lambda$createDockerImage$21(MicronautDockerPlugin.java:173)
	at org.gradle.api.internal.DefaultMutationGuard$1.execute(DefaultMutationGuard.java:45)
	at org.gradle.api.internal.DefaultMutationGuard$1.execute(DefaultMutationGuard.java:45)
	at org.gradle.internal.code.DefaultUserCodeApplicationContext$CurrentApplication$1.execute(DefaultUserCodeApplicationContext.java:122)
	at org.gradle.api.internal.DefaultCollectionCallbackActionDecorator$BuildOperationEmittingAction$1.run(DefaultCollectionCallbackActionDecorator.java:110)
	at org.gradle.internal.operations.DefaultBuildOperationRunner$1.execute(DefaultBuildOperationRunner.java:29)
	at org.gradle.internal.operations.DefaultBuildOperationRunner$1.execute(DefaultBuildOperationRunner.java:26)
	at org.gradle.internal.operations.DefaultBuildOperationRunner$2.execute(DefaultBuildOperationRunner.java:66)
	at org.gradle.internal.operations.DefaultBuildOperationRunner$2.execute(DefaultBuildOperationRunner.java:59)
	at org.gradle.internal.operations.DefaultBuildOperationRunner.execute(DefaultBuildOperationRunner.java:157)
	at org.gradle.internal.operations.DefaultBuildOperationRunner.execute(DefaultBuildOperationRunner.java:59)
	at org.gradle.internal.operations.DefaultBuildOperationRunner.run(DefaultBuildOperationRunner.java:47)
	at org.gradle.internal.operations.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:68)
	at org.gradle.api.internal.DefaultCollectionCallbackActionDecorator$BuildOperationEmittingAction.execute(DefaultCollectionCallbackActionDecorator.java:107)
	at org.gradle.api.internal.DefaultNamedDomainObjectCollection$AbstractDomainObjectCreatingProvider.configure(DefaultNamedDomainObjectCollection.java:909)
	at io.micronaut.gradle.docker.MicronautDockerPlugin.lambda$createDockerImage$22(MicronautDockerPlugin.java:171)
	at io.micronaut.gradle.docker.MicronautDockerPlugin.lambda$createDockerImage$23(MicronautDockerPlugin.java:171)
	at io.micronaut.gradle.docker.MicronautDockerPlugin.lambda$withBuildStrategy$24(MicronautDockerPlugin.java:186)
	...

[melix]

Thanks for the PR. However it seems curious that you have the problem on a bom project. It sounds as if the Micronaut plugins are applied on this project, which shouldn't be the case, right?

[rorueda]

That is why I thought the message is so misleading. The only plugins applied to the bom are java-platform and com.google.osdetector, but the project for which I actually executed the tasks task applies the micronaut.application and has the bom as a dependency. I tested removing the bom, but then I had the same error on other plugins.