suggestion

[itlonewolf]

you can use gradle.buildFinished instead check whether the task is last or not

void buildFinished(Closure closure)
    Adds a closure to be called when the build is completed. All selected tasks have been executed. A BuildResult instance is passed to the closure as a parameter.

https://docs.gradle.org/3.3/dsl/org.gradle.api.invocation.Gradle.html

[tomorrowkey]

looks good :)