RFR: JDK-8216489: Issues with ModulePackages attribute generation on incremental build

[Erik Joelsson]

The incremental build of exploded-image-optimize is broken. This is 
caused by a small typo in the prerequisites declaration for the recipe.

Bug: https://bugs.openjdk.java.net/browse/JDK-8216489
Webrev: http://cr.openjdk.java.net/~erikj/8216489/webrev.01/

/Erik