[hack] Fix error in libancillary gnu-variable-sized-type-not-at-end
[hack] Fix error in libancillary gnu-variable-sized-type-not-at-end

Summary: clang doesn't support variable-sized structs in the non-terminal position

Reviewed By: int3

Differential Revision: D2556710

fb-gh-sync-id: 6a8cb1ff9bdfb97923544eb321081ab18dffa3cd

jdelStrother/flow,d14b3l/flow,samwgoldman/flow,jeffmo/flow,popham/flow,jgrund/flow,facebook/flow,jamesgpearce/flow,TiddoLangerak/flow,MichaelDeBoey/flow,chenglou/flow,jeffmo/flow,AgentME/flow,shiftcars/flow,chenglou/flow,chenglou/flow,graue/flow,ForbesLindesay/flow,ylu1317/flow,JonathanUsername/flow,shiftcars/flow,AgentME/flow,ForbesLindesay/flow,OCamlPro/flow,OCamlPro/flow,jgrund/flow,jamesgpearce/flow,claudiopro/flow,AprilArcus/flow,jdelStrother/flow,jdelStrother/flow,graue/flow,TiddoLangerak/flow,nmote/flow,gabelevi/flow,graue/flow,popham/flow,claudiopro/flow,claudiopro/flow,AprilArcus/flow,ylu1317/flow,jamesgpearce/flow,nmote/flow,d14b3l/flow,AgentME/flow,AgentME/flow,gabelevi/flow,samwgoldman/flow,OCamlPro/flow,samwgoldman/flow,popham/flow,shiftcars/flow,ForbesLindesay/flow,chenglou/flow,jgrund/flow,popham/flow,cesarandreu/flow,jeffmo/flow,graue/flow,d14b3l/flow,popham/flow,jdelStrother/flow,shiftcars/flow,AprilArcus/flow,facebook/flow,fletcherw/flow,graue/flow,cesarandreu/flow,fletcherw/flow,nmote/flow,mroch/flow,JonathanUsername/flow,facebook/flow,gabelevi/flow,fletcherw/flow,fletcherw/flow,mroch/flow,nmote/flow,samwgoldman/flow,gabelevi/flow,jeffmo/flow,AprilArcus/flow,cesarandreu/flow,shiftcars/flow,popham/flow,samwgoldman/flow,gabro/flow,JonathanUsername/flow,graue/flow,gabelevi/flow,gabro/flow,jgrund/flow,gabro/flow,gabro/flow,jamesgpearce/flow,jamesgpearce/flow,popham/flow,fletcherw/flow,jeffmo/flow,nmote/flow,nmote/flow,shiftcars/flow,JonathanUsername/flow,chenglou/flow,samwgoldman/flow,jdelStrother/flow,OCamlPro/flow,MichaelDeBoey/flow,ylu1317/flow,chenglou/flow,ylu1317/flow,ForbesLindesay/flow,TiddoLangerak/flow,JonathanUsername/flow,TiddoLangerak/flow,mroch/flow,facebook/flow,mroch/flow,d14b3l/flow,MichaelDeBoey/flow,gabelevi/flow,jamesgpearce/flow,nmote/flow,samwgoldman/flow,ylu1317/flow,JonathanUsername/flow,TiddoLangerak/flow,gabelevi/flow,facebook/flow,jgrund/flow,jgrund/flow,AgentME/flow,d14b3l/flow,JonathanUsername/flow,ForbesLindesay/flow,mroch/flow,facebook/flow,claudiopro/flow,ForbesLindesay/flow,gabro/flow,mroch/flow,MichaelDeBoey/flow,jamesgpearce/flow,mroch/flow,claudiopro/flow,fletcherw/flow,d14b3l/flow,gabro/flow,jeffmo/flow,AprilArcus/flow,jdelStrother/flow,MichaelDeBoey/flow,AprilArcus/flow,facebook/flow,cesarandreu/flow