QNativeSocketEngine: disable sign-compare warning-turned-error on Clang

On the WASM platform, the macro CMDG_NEXTHDR, which is not under our
control, emits a warning about comparing ulong and long with each
other, which -Werror turns into an error:

  qnativesocketengine_unix.cpp:1004:24: error: comparison of integers of different signs: 'unsigned long' and 'long' [-Werror,-Wsign-compare]
    cmsgptr = CMSG_NXTHDR(&msg, cmsgptr)) {
              ^~~~~~~~~~~~~~~~~~~~~~~~~~
  emsdk/emscripten/1.38.30/system/include/libc/sys/socket.h:286:44: note: expanded from macro 'CMSG_NXTHDR'
    __CMSG_LEN(cmsg) + sizeof(struct cmsghdr) >= __MHDR_END(mhdr) - (unsigned char *)(cmsg) \
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fix by locally disabling the warning.

Change-Id: Ia2ed4318b2ef679b84ac8544835d1e383568ccac
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

0 files changed, 0 insertions, 0 deletions