Move core/scripts to build/scripts so that platform can use them.

Source/build/scripts/templates/InternalRuntimeFlags.idl.tmpl

 {% from "macros.tmpl" import license -%}
 {{ license() }}
 
 [
 ] interface InternalRuntimeFlags {
 {%- for feature in features if not feature.custom %}
 {#-
     Currently assuming that runtime flags cannot be changed after startup
     it's possible that some can be and should be conditionally readonly.
 #}
     {% if feature.condition -%} [Conditional={{feature.condition}}] {% endif -%}
     readonly attribute boolean {{feature.first_lowered_name}}Enabled;
 {%- endfor %}
 };