RFR: JDK-8025869: make docs doesn't regenerate docs correctly after changing API doc comments in jaxp sources

[Erik Joelsson]

Please review this fix for SetupZipArchive. The dependency list ended up 
empty if the SUFFIXES parameter wasn't set. This caused src.zip to not 
get updated when source files were changed.

http://cr.openjdk.java.net/~erikj/8025869/webrev.root.01/
/Erik