[web-service] ot-client: add needed header for fd_set() call (#1326)
[web-service] ot-client: add needed header for fd_set() call (#1326)

The select.h header file is needed for fd_set(). Depending on the
compiler and libc combinations this will result in an error when
not included. I saw the error with gcc and musl on our builds.

Signed-off-by: Stefan Schmidt <34aa0f04dfc141f9510278c1e3d9c2cce249189e@huawei.com>
openthread/ot-br-posix,openthread/ot-br-posix,openthread/borderrouter,openthread/borderrouter,openthread/borderrouter,openthread/ot-br-posix,openthread/borderrouter,openthread/borderrouter,openthread/ot-br-posix,openthread/ot-br-posix,openthread/borderrouter,openthread/ot-br-posix