Small testcase (on cygwin, but this should also happen on MacOSX with HFS+)

-- t_dcache_1.mk --
SHELL*:=/bin/sh 
SHELLFLAGS*:=-ce

test.file :
	@echo "Building $@"
-- t_dcache_1.mk --

$ rm -f test.file ; touch TEST.file

$ ./dmake/dmake.exe -rf t_dcache_1.mk 
"Building test.file"

but if the directory cache is disabled:
$ ./dmake/dmake.exe -d -rf t_dcache_1.mk 
`test.file' is up to date


This is obviously only an issue for case insensitive (but preserving) file
systems.

(While looking at this I found that the native W32 version doesn't do any
directory caching at all, but that is clearly another issue.)