Add source roots to modules 'builtins' and 'runtime.jvm'

This is done to be able to write code in the module 'reflection.jvm' in the IDE
without lots of unresolved errors and such

.idea/libraries/kotlin_runtime.xml

@@ -7,8 +7,6 @@
     <JAVADOC />
     <SOURCES>
       <root url="file://$PROJECT_DIR$/libraries/stdlib/src" />
-      <root url="file://$PROJECT_DIR$/core/builtins/src" />
-      <root url="file://$PROJECT_DIR$/core/runtime.jvm/src" />
     </SOURCES>
   </library>
 </component>