test/stdout: fix strcmp non-\0 string
test/stdout: fix strcmp non-\0 string

After copying len(str) bytes of a string, the copy won't necessary have
\0 terminator, that makes test_pipe_io_fixed() to fail. Use memcmp().

Signed-off-by: Pavel Begunkov <8608d41fe50396a9dbd36e830be65ba791e26c05@gmail.com>
Signed-off-by: Jens Axboe <cd8c6775e60d6f67a6984377324e5290df3d5358@kernel.dk>

axboe/liburing,axboe/liburing,axboe/liburing