Fix incremental execution of GatherLicenseTask: the task now is non-incremental in case overides are present

Ideally the task should be incremental in all the cases, however, override tracking is not implemented yet.

Author: vlsi

plugins/license-gather-plugin/src/main/kotlin/com/github/vlsi/gradle/license/GatherLicenseTask.kt

@@ -97,7 +97,7 @@ open class GatherLicenseTask @Inject constructor(
 ) : DefaultTask() {
     init {
         // TODO: capture [licenseOverrides] as input
-        outputs.upToDateWhen { false }
+        outputs.upToDateWhen { licenseOverrides.isEmpty() }
     }
 
     @InputFiles

plugins/license-gather-plugin/src/main/kotlin/com/github/vlsi/gradle/license/LicenseOverrides.kt

@@ -24,6 +24,8 @@ class LicenseOverrides {
     private val map = mutableMapOf<String, LicenseOverride>()
     private val usedOverrides = mutableSetOf<String>()
 
+    fun isEmpty(): Boolean = map.isEmpty()
+
     val unusedOverrides: Set<String> get() = map.keys.minus(usedOverrides)
 
     fun configurationComplete() {