Better check when to apply old syntax for configuration (KT-28513, KT-22571)

^KT-28513 Fixed

idea/testData/configuration/gsk/missedLibrary/build_after.gradle.kts

@@ -1,11 +1,7 @@
 import org.gradle.api.JavaVersion.VERSION_1_7
 import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 
-val kotlin_version: String by extra
-
 buildscript {
-    var kotlin_version: String by extra
-    kotlin_version = "$VERSION$"
     repositories {
         mavenCentral()
     }
@@ -17,6 +13,7 @@ buildscript {
 
 plugins {
     application
+    kotlin("jvm") version "$VERSION$"
 }
 
 apply {
@@ -33,7 +30,7 @@ repositories {
 
 dependencies {
     testCompile("junit:junit:4.12")
-    compile(kotlinModule("stdlib-jdk8", kotlin_version))
+    compile(kotlin("stdlib-jdk8"))
 }
 val compileKotlin: KotlinCompile by tasks
 compileKotlin.kotlinOptions {