Fix changes in Android layout resources breaks incremental compilation

This only happens when project has 'kotlin-android-extensions' plugin
applied and 'experimental = true' flag is set. On changes in android
layout resources task was running full compilation instead running
incrementally.

^KT-51177 Fixed

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

@@ -996,6 +996,41 @@ fun getSomething() = 10
         }
     }
 
+    // KT-51177: when experimental flag is enabled
+    @Test
+    fun testIncrementalBuildAfterResourceChangeAndroidExtensions() {
+        val project = Project("AndroidExtensionsProject")
+        project.setupWorkingDir()
+
+        project.projectDir.resolve("app/build.gradle").appendText(
+            """
+            |
+            |androidExtensions {
+            |    experimental = true
+            |}
+            """.trimMargin()
+        )
+
+        project.build("assembleDebug") {
+            assertSuccessful()
+            assertTasksExecuted(":app:compileDebugKotlin")
+        }
+
+        project.projectDir
+            .resolve("app/src/main/res/layout/activity_main.xml")
+            .modify {
+                it.replace("android:layout_width=\"wrap_content\"", "android:layout_width=\"match_parent\"")
+            }
+
+        project.build("assembleDebug") {
+            assertSuccessful()
+            assertTasksExecuted(":app:compileDebugKotlin")
+            assertContainsRegex(
+                "compilerMode=INCREMENTAL_COMPILER.*areFileChangesKnown=true.*app/build/kotlin".toRegex()
+            )
+        }
+    }
+
     @Test
     fun testAndroidDaggerIC() {
         val project = Project("AndroidDaggerProject")

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/targets/android/internal/AndroidSubplugin.kt

@@ -204,6 +204,7 @@ class AndroidSubplugin :
                 it.inputs.files(getLayoutDirectories(project, resDirectories))
                     .withPathSensitivity(PathSensitivity.RELATIVE)
                     .withPropertyName("androidExtensionLayoutsFrom$name")
+                    .skipWhenEmpty(true)
                     .run {
                         if (GradleVersion.current() >= GradleVersion.version("6.8")) {
                             ignoreEmptyDirectories()