This task will examine each of the source files against each of the target
files. If any target files are out of date with respect to any of the source
files, all targets are removed. If any files named in a (src or target)
filelist do not exist, all targets are removed.
Hint: If missing files should be ignored, specify them as include patterns
in filesets, rather than using filelists.
This task attempts to optimize speed of dependency checking. It will stop
after the first out of date file is found and remove all targets, rather
than exhaustively checking every source vs target combination unnecessarily.