[Gradle] Add IT that useExperimentalAnnotation produces deprecation warn

#KT-38111 Fixed

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

@@ -207,4 +207,16 @@ class SimpleKotlinGradleIT : KGPBaseTest() {
             build("assemble")
         }
     }
+
+    @GradleTest
+    @DisplayName("useExperimentalAnnotation should produce deprecation warning")
+    fun testUseExperimentalAnnotationShouldProduceWarning(gradleVersion: GradleVersion) {
+        project("optInAnnotation", gradleVersion, buildOptions = defaultBuildOptions.copy(logLevel = LogLevel.DEBUG)) {
+            build("assemble") {
+                assertOutputContains("-Xopt-in=kotlin.RequiresOptIn")
+                assertOutputContains("-Xopt-in=FooAnnotation")
+                assertOutputContains("is deprecated and will be removed in next major releases")
+            }
+        }
+    }
 }

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/optInAnnotation/build.gradle

@@ -0,0 +1,19 @@
+plugins {
+    id "org.jetbrains.kotlin.jvm"
+}
+
+repositories {
+    mavenLocal()
+    mavenCentral()
+}
+
+kotlin {
+    sourceSets {
+        main {
+            languageSettings {
+                useExperimentalAnnotation("kotlin.RequiresOptIn")
+                useExperimentalAnnotation("FooAnnotation")
+            }
+        }
+    }
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/optInAnnotation/src/main/kotlin/foo.kt

@@ -0,0 +1,11 @@
+@Target(AnnotationTarget.CLASS)
+@Retention(AnnotationRetention.BINARY)
+@RequiresOptIn
+annotation class FooAnnotation
+
+@FooAnnotation
+class FooClass
+
+fun foo() {
+    FooClass()
+}