Makefile: build t/fio-dedupe only if zlib support is found

Makefile: build t/fio-dedupe only if zlib support is found

df284fbdc23974c931865a8ddb7d171606b3c778 added zlib support as a
requirement for building fio-dedupe.

The current patch changes the Makefile to avoid trying to build
fio-dedupe when zlib support is not present.

Link: https://lore.kernel.org/fio/51b79acb-c314-143b-514c-a22ff9462829@gmail.com/T/#u
Reported-by: Professor Pro <annivation@gmail.com>
Signed-off-by: Vincent Fu <vincent.fu@samsung.com>
Link: https://lore.kernel.org/r/20220128214611.165312-1-vincent.fu@samsung.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>