unix: disable clang variable length array warning

PR-URL: https://github.com/libuv/libuv/pull/1892
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

src/unix/stream.c

@@ -1121,6 +1121,7 @@ static int uv__stream_recv_cmsg(uv_stream_t* stream, struct msghdr* msg) {
 #ifdef __clang__
 # pragma clang diagnostic push
 # pragma clang diagnostic ignored "-Wgnu-folding-constant"
+# pragma clang diagnostic ignored "-Wvla-extension"
 #endif
 
 static void uv__read(uv_stream_t* stream) {