[Omake] depending on the contents of a directory

[Mike Furr]

I've started adding some system tests to one of my projects and I would 
like to get OMake to rerun the test suite whenever the input files 
change (including adding new ones).  Is this possible?
A first attempt was:

test_suite.results: $(TEST_PROGRAM) :value: $(stat $(dir [...])).mtime
	./$(TEST_PROGRAM) |& tee $@

where [...] is the directory where I want to be able to add/modify the 
test data and have omake rerun the tests (with its -P goodness). 
However, this gives:

    Non digestable value:
       class Stat Object
       Contact the OMake team at omake at metaprl.org if you think this 
should be supported

So, if that rule is indeed a good way to handle this, "I think this 
should be supported" :-D, but I'm not even sure if it is.  For instance 
will OMake rerun the stat when the directory actually changes?  Is there 
a better (supported?) way to do this?

Thanks!
-mike