[Gradle] Use compiler argument -opt-in instead of '-Xopt-in'

#KT-35832 Fixed

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

@@ -748,8 +748,8 @@ class NewMultiplatformIT : BaseGradleIT() {
                 assertTasksExecuted(":$it")
                 assertContains(
                     "-XXLanguage:+InlineClasses",
-                    "-progressive", "-Xopt-in=kotlin.ExperimentalUnsignedTypes",
-                    "-Xopt-in=kotlin.contracts.ExperimentalContracts",
+                    "-progressive", "-opt-in=kotlin.ExperimentalUnsignedTypes",
+                    "-opt-in=kotlin.contracts.ExperimentalContracts",
                     "-Xno-inline"
                 )
             }

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

@@ -213,8 +213,8 @@ class SimpleKotlinGradleIT : KGPBaseTest() {
     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("-opt-in=kotlin.RequiresOptIn")
+                assertOutputContains("-opt-in=FooAnnotation")
                 assertOutputContains("is deprecated and will be removed in next major releases")
             }
         }

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/sources/DefaultLanguageSettingsBuilder.kt

@@ -138,7 +138,7 @@ internal fun applyLanguageSettingsToKotlinOptions(
         }
     
         languageSettingsBuilder.optInAnnotationsInUse.forEach { annotationName ->
-            add("-Xopt-in=$annotationName")
+            add("-opt-in=$annotationName")
         }
 
         if (languageSettingsBuilder is DefaultLanguageSettingsBuilder) {

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/targets/native/tasks/KotlinNativeTasks.kt

@@ -463,7 +463,7 @@ constructor(
             add("-XXLanguage:+$featureName")
         }
         optInAnnotationsInUse.forEach { annotationName ->
-            add("-Xopt-in=$annotationName")
+            add("-opt-in=$annotationName")
         }
     }
 
@@ -629,7 +629,7 @@ constructor(
                 add("-XXLanguage:+$featureName")
             }
             it.optInAnnotationsInUse.forEach { annotationName ->
-                add("-Xopt-in=$annotationName")
+                add("-opt-in=$annotationName")
             }
         }
     }