iowatcher: link with -lrt

Some C libraries (notably uClibc) have the posix_spawn*() functions in
librt, so let's link iowatcher with -lrt.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
1 file changed