Prohibit JVM target 1.6

But still compile stdlib, reflect, kotlin.test and scripting runtimes
with JVM target 1.6 to simplify migration from Kotlin 1.6 to 1.7.

 #KT-45165 Fixed

libraries/reflect/api/build.gradle

@@ -29,6 +29,7 @@ dependencies {
     compileOnly project(':core:descriptors.runtime')
     compileOnly project(':core:util.runtime')
     compileOnly "org.jetbrains:annotations:13.0"
+    kotlinCompilerClasspath project(':libraries:tools:stdlib-compiler-classpath')
 }
 
 if (includeJava9) {