Plugin build fails with Gradle 7

[carlosame]

I attempted to build the moduleplugin with Java 16 and Gradle 7.0.2, failed with the typical resource duplicate error:

$ gradle build

 [...]

> Task :processResources FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':processResources'.
> Entry META-INF/gradle-plugins/org.javamodularity.moduleplugin.properties is a duplicate but no duplicate handling strategy has been set. Please refer to https://docs.gradle.org/7.0.2/dsl/org.gradle.api.tasks.Copy.html#org.gradle.api.tasks.Copy:duplicatesStrategy for details.

As the error message suggests, setting duplicatesStrategy = 'exclude' is the most obvious way to deal with the issue.

[siordache]

Thanks for the PR! Fixed in 1.8.7.