Fix build of SysUio portability header

Summary: When I moved the change internally, I failed to add the `#include` that was required :(

Reviewed By: yfeldblum

Differential Revision: D5366037

fbshipit-source-id: 7ddf8fc0b7a0468d0831e886d8025c1893f7f8ae

folly/portability/SysUio.cpp

@@ -20,6 +20,7 @@
 #include <stdio.h>
 
 #include <folly/ScopeGuard.h>
+#include <folly/portability/Sockets.h>
 #include <folly/portability/SysFile.h>
 #include <folly/portability/Unistd.h>