Fix changes in Android Java sources prevents incremental compilation

Such sources are attached to kapt generate stubs task to re-trigger it
on Java sources change, but they are not participate in actual stubs
generation.

^KT-50664 Fixed

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/Kapt3AndroidIT.kt

@@ -376,6 +376,57 @@ abstract class Kapt3AndroidIT : BaseGradleIT() {
         }
     }
 
+    @Test
+    fun generateStubsTaskShouldRunIncrementallyOnChangesInAndroidVariantJavaSources() {
+        with(Project("android-dagger", directoryPrefix = "kapt2")) {
+            setupWorkingDir()
+
+            val javaFile = projectDir.resolve("app/src/main/java/com/example/dagger/kotlin/Utils.java")
+            javaFile.writeText(
+                //language=Java
+                """
+                package com.example.dagger.kotlin;
+
+                class Utils {
+                    public String oneMethod() {
+                        return "fake!";
+                    }
+                }
+                """.trimIndent()
+            )
+
+            build(":app:kaptDebugKotlin") {
+                assertSuccessful()
+                assertTasksExecuted(":app:kaptGenerateStubsDebugKotlin")
+            }
+
+            javaFile.writeText(
+                //language=Java
+                """
+                package com.example.dagger.kotlin;
+
+                class Utils {
+                    public String oneMethod() {
+                        return "fake!";
+                    }
+                    
+                    public void anotherMethod() {
+                        int one = 1;
+                    }
+                }
+                """.trimIndent()
+            )
+
+            build(":app:kaptDebugKotlin") {
+                assertSuccessful()
+                assertTasksExecuted(":app:kaptGenerateStubsDebugKotlin")
+                assertNotContains(
+                    "The input changes require a full rebuild for incremental task ':app:kaptGenerateStubsDebugKotlin'."
+                )
+            }
+        }
+    }
+
     private fun setupDataBinding(project: Project) {
         project.setupWorkingDir()
 

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/internal/kapt/KaptGenerateStubsTask.kt

@@ -22,6 +22,7 @@ import org.gradle.api.file.DirectoryProperty
 import org.gradle.api.provider.Property
 import org.gradle.api.provider.Provider
 import org.gradle.api.tasks.*
+import org.gradle.work.Incremental
 import org.gradle.workers.WorkerExecutor
 import org.jetbrains.kotlin.cli.common.arguments.K2JVMCompilerArguments
 import org.jetbrains.kotlin.gradle.dsl.KotlinJvmOptionsImpl
@@ -115,6 +116,7 @@ abstract class KaptGenerateStubsTask @Inject constructor(
     @get:InputFiles
     @get:IgnoreEmptyDirectories
     @get:PathSensitive(PathSensitivity.RELATIVE)
+    @get:Incremental
     abstract val additionalSources: ConfigurableFileCollection
 
     override fun source(vararg sources: Any): SourceTask {