RFR: JDK-8215239: Make deletes images/jdk/bin/java if something goes wrong

[Erik Joelsson]

If something goes wrong in the recipe for creating the jdk image, make 
will automatically delete the target of the recipe, which happens to be 
bin/java in the image. This is unfortunate, because that file is rather 
useful when troubleshooting what went wrong.

I propose to fix this by changing the target to the release file in the 
root of the image instead.

Bug: https://bugs.openjdk.java.net/browse/JDK-8215239

Webrev: http://cr.openjdk.java.net/~erikj/8215239/webrev.01/

/Erik