RFR: JDK-8232723: make the resource file main.wxs over-ridable

[Alexey Semenyuk]

Looks good.

It would be good to have a test for this change as a part of this fix or 
as a follow up CR.

- Alexey

On 10/22/2019 2:50 PM, Andy Herrick wrote:
> Please review the jpackage fix for bug [1] at [2].
>
> This is a fix for the JDK-8200758-branch branch of the open sandbox 
> repository (jpackage).
>
> use createResource() to get an over-ridable resource.
>
> [1] https://bugs.openjdk.java.net/browse/JDK-8232723
>
> [2] http://cr.openjdk.java.net/~herrick/8232723/webrev.01
>
> /Andy
>