Support progressive mode via "-progressive"

#KT-25862 Fixed

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

@@ -293,7 +293,7 @@ class NewMultiplatformIT : BaseGradleIT() {
 
         build("compileKotlinJvm6") {
             assertSuccessful()
-            assertContains("-language-version 1.3", "-api-version 1.3", "-XXLanguage:+InlineClasses", " -Xprogressive")
+            assertContains("-language-version 1.3", "-api-version 1.3", "-XXLanguage:+InlineClasses", " -progressive")
         }
     }
 

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

@@ -62,7 +62,7 @@ internal fun applyLanguageSettingsToKotlinTask(
     apiVersion = apiVersion ?: languageSettingsBuilder.apiVersion
 
     if (languageSettingsBuilder.progressiveMode) {
-        freeCompilerArgs += "-Xprogressive"
+        freeCompilerArgs += "-progressive"
     }
 
     languageSettingsBuilder.enabledLanguageFeatures.forEach { featureName ->