Fix empty Android layout directories are not ignored

Kotlin Android extensions plugin adds layout directories as input to
KotlinCompile task when experimental flag is enabled. This breaks
cache relocation.

^KT-48849 Fixed

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

@@ -194,6 +194,39 @@ class BuildCacheRelocationIT : KGPBaseTest() {
         )
     }
 
+    @DisplayName("KT-48849: Kotlin compile should ignore empty layout resource directories added by kotlin android extensions")
+    @GradleTestVersions(minVersion = TestVersions.Gradle.G_6_8)
+    @GradleTest
+    fun compileIgnoreEmptyAndroidResLayoutDirs(gradleVersion: GradleVersion) {
+        val (firstProject, secondProject) = prepareTestProjects(
+            "AndroidExtensionsProject",
+            gradleVersion,
+            defaultBuildOptions.copy(androidVersion = TestVersions.AGP.AGP_42)
+        ) {
+            it.subProject("app").buildGradle.append(
+                """
+                |
+                |androidExtensions {
+                |    experimental = true
+                |}
+                """.trimMargin()
+            )
+        }
+
+        firstProject
+            .subProject("app")
+            .projectPath
+            .resolve("src/main/res/layout-ar")
+            .createDirectory()
+
+        checkBuildCacheRelocation(
+            firstProject,
+            secondProject,
+            listOf("assembleDebug"),
+            listOf(":app:compileDebugKotlin")
+        )
+    }
+
     @DisplayName("with native project")
     @GradleTest
     @DisabledOnOs(OS.WINDOWS, disabledReason = "remove after fix of KT-48283")

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

@@ -19,6 +19,7 @@ import org.gradle.api.tasks.PathSensitivity
 import org.gradle.api.tasks.TaskProvider
 import org.gradle.api.tasks.compile.AbstractCompile
 import org.gradle.tooling.provider.model.ToolingModelBuilderRegistry
+import org.gradle.util.GradleVersion
 import org.jetbrains.kotlin.gradle.dsl.KotlinCommonOptions
 import org.jetbrains.kotlin.gradle.model.builder.KotlinAndroidExtensionModelBuilder
 import org.jetbrains.kotlin.gradle.plugin.*
@@ -200,7 +201,16 @@ class AndroidSubplugin :
             )
 
             kotlinCompile.configure {
-                it.inputs.files(getLayoutDirectories(project, resDirectories)).withPathSensitivity(PathSensitivity.RELATIVE)
+                it.inputs.files(getLayoutDirectories(project, resDirectories))
+                    .withPathSensitivity(PathSensitivity.RELATIVE)
+                    .withPropertyName("androidExtensionLayoutsFrom$name")
+                    .run {
+                        if (GradleVersion.current() >= GradleVersion.version("6.8")) {
+                            ignoreEmptyDirectories()
+                        } else {
+                            this!!
+                        }
+                    }
             }
         }