Fix build of SysUio portability header
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

facebook/folly,rklabs/folly,facebook/folly,rklabs/folly,Orvid/folly,facebook/folly,rklabs/folly,rklabs/folly,facebook/folly,facebook/folly,Orvid/folly,Orvid/folly,Orvid/folly,Orvid/folly,rklabs/folly