Improve kapt arguments & javac options usability with Kotlin DSL

Issue #KT-21596 Fixed

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kapt2/arguments/build.gradle

@@ -30,6 +30,8 @@ kapt {
         arg("containsColon", "a:b")
         arg("containsEquals", "a=b")
         arg("startsWithColon", ":a")
+    }
+    arguments {
         arg("startsWithEquals", "=a")
         arg("endsWithColon", "a:")
         arg("endsWithEquals", "a:")
@@ -38,6 +40,8 @@ kapt {
 
     javacOptions {
         option("-Xmaxerrs", 500)
+    }
+    javacOptions {
         option("-Xlint:all")
     }
 }