RFR: JDK-8037238: JDK 9 images don't rebuild when access bridge jars rebuild

[Tim Bell]

Hi Erik:

> When rebuilding after touching a java source file in AccessBridge, the 
> classes were recompiled but the jars were not rebuilt. This was caused 
> by a bug in the macro CacheFind. The cache in this case contained the 
> directory $(JDK_OUTPUTDIR)/classes. The jar was built from the src dir 
> $(JDK_OUTPUTDIR)/classes_ab. The matching code found the latter to be 
> a subdir of the former and so chose to use the cache and of course 
> found nothing. I fixed the test to either match with a trailing slash 
> or make an exact match.
>
> I also added a warning in SetupArchive so that we will catch empty 
> dependency lists faster next time.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8037238
> Webrev: http://cr.openjdk.java.net/~erikj/8037238/webrev.root.01/

Very subtle.  Looks good to me.

Tim