Fix fatal gradle 7 compile error.

[jameshilliard]

Fixes:

Caused by: groovy.lang.MissingPropertyException: Could not get unknown property 'compile' for configuration container of type org.gradle.api.internal.artifacts.configurations.DefaultConfigurationContainer.
        at org.gradle.internal.metaobject.AbstractDynamicObject.getMissingProperty(AbstractDynamicObject.java:85)
        at org.gradle.internal.metaobject.AbstractDynamicObject.getProperty(AbstractDynamicObject.java:62)
        at org.gradle.api.internal.artifacts.configurations.DefaultConfigurationContainer_Decorated.getProperty(Unknown Source)
        at com.devsoap.plugin.tasks.CompileWidgetsetTask$_closure4.doCall(CompileWidgetsetTask.groovy:228)

This issue appears to prevent the plugin from being used with gradle 7 which appears will be required for java 16 support.

[jameshilliard]

FYI this failure appears to be due to the gradle version being too old, so i think #546 is probably also needed for tests to pass.

[jameshilliard]

@johndevs Could you take a look at this? It would be good to have this fixed so that jdk16/gradle7 upgrades aren't blocked for projects that depend on this plugin.