test/io_uring_register: fix -Wimplicit-function-declaration of memfd_create

On some systems, there is no `memfd_create` function. This commit
fixes this:
```
       CC io_uring_register
  io_uring_register.c: In function 'test_shmem':
  io_uring_register.c:514:10: warning: implicit declaration of function 'memfd_create' [-Wimplicit-function-declaration]
    memfd = memfd_create("uring-shmem-test", 0);
            ^
```

Fix for this is based on an answer on Stack Overflow [1].

On Jun 16 '19 at 5:12, mosvy wrote:
> On older systems, you'll have to include linux/memfd.h for the MFD_
> defines, and call memfd_create() via the the syscall(2) wrapper
> (and include unistd.h and sys/syscall.h for it work).
>

Link: https://stackoverflow.com/a/56616264/7275114 [1]
Reported-by: Louvian Lyndal <louvianlyndal@gmail.com>
Tested-by: Louvian Lyndal <louvianlyndal@gmail.com>
Signed-off-by: Ammar Faizi <ammarfaizi2@gmail.com>

0 files changed, 0 insertions, 0 deletions