Use -opt-in instead of -Xopt-in in comments and scripts

libraries/kotlin.test/common/build.gradle

@@ -17,14 +17,14 @@ configureSourcesJar()
 configureJavadocJar()
 
 tasks.withType(org.jetbrains.kotlin.gradle.dsl.KotlinCompile) {
-    kotlinOptions.freeCompilerArgs += ["-Xallow-kotlin-package", "-Xopt-in=kotlin.RequiresOptIn"]
+    kotlinOptions.freeCompilerArgs += ["-Xallow-kotlin-package", "-opt-in=kotlin.RequiresOptIn"]
 }
 
 compileKotlinCommon {
     kotlinOptions {
         freeCompilerArgs += [
                 "-module-name", project.name,
-                "-Xopt-in=kotlin.contracts.ExperimentalContracts",
+                "-opt-in=kotlin.contracts.ExperimentalContracts",
         ]
     }
 }

libraries/kotlin.test/js/build.gradle

@@ -16,8 +16,8 @@ dependencies {
 compileKotlin2Js {
     kotlinOptions.freeCompilerArgs = [
             "-Xallow-kotlin-package",
-            "-Xopt-in=kotlin.contracts.ExperimentalContracts",
-            "-Xopt-in=kotlin.RequiresOptIn",
+            "-opt-in=kotlin.contracts.ExperimentalContracts",
+            "-opt-in=kotlin.RequiresOptIn",
     ]
     kotlinOptions {
         moduleKind = "umd"

libraries/kotlin.test/jvm/build.gradle

@@ -42,9 +42,9 @@ configureJavadocJar()
 compileKotlin {
     kotlinOptions.freeCompilerArgs = [
         "-Xallow-kotlin-package",
-        "-Xopt-in=kotlin.contracts.ExperimentalContracts",
+        "-opt-in=kotlin.contracts.ExperimentalContracts",
         "-Xsuppress-deprecated-jvm-target-warning",
-        "-Xopt-in=kotlin.RequiresOptIn",
+        "-opt-in=kotlin.RequiresOptIn",
     ]
     kotlinOptions.moduleName = project.archivesBaseName
 }
@@ -53,7 +53,7 @@ compileTestKotlin {
     kotlinOptions.freeCompilerArgs = [
         "-Xallow-kotlin-package",
         "-Xsuppress-deprecated-jvm-target-warning",
-        "-Xopt-in=kotlin.RequiresOptIn",
+        "-opt-in=kotlin.RequiresOptIn",
     ]
 }