diagnostics: fix socket includes for MinGW host [PR122666]

diagnostics: fix socket includes for MinGW host [PR122666]

The commit "diagnostics: add experimental SARIF JSON-RPC notifications
for IDEs [PR115970]"

https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=8a155c170b443e332b3db4922f0f0d588a17604f

introduces a regression when building the toolchain for the
aarch64-w64-mingw32 host, at least. It is most likely the same for
*-*-mingw32 targets.

This patch resolves the issue when using sockets for SARIF JSON-RPC
notifications on MinGW host and adds the required socket library to the
host file for *-*-mingw.

Signed-off-by: Evgeny Karpov <evgeny@kmaps.co>
gcc/ChangeLog:
	PR diagnostics/122666
	* config/i386/x-mingw32 (LIBS): Add -lws2_32
	* diagnostics/sarif-sink.cc: Move sockets includes to before
	config.h and support __MINGW32__.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>