check only one event is returned in kevent() call to allow type coercion

Author: frankeh

src/shims/linux_stubs.c

@@ -169,7 +169,11 @@ int kevent64(int kq, /*const*/ struct kevent64_s *changelist, int nchanges, stru
          }
      }
 #endif
-     return kevent(kq,(struct kevent*) changelist,nchanges,(struct kevent*) eventlist,nevents,timeout);
+     // eventlist can not return more than 1 event type coersion doesn't work
+     int rc = kevent(kq,(struct kevent*) changelist,nchanges,(struct kevent*) eventlist,nevents,timeout);
+     if (rc > 1) 
+         LINUX_PORT_ERROR();
+     return rc;
 }
 
 /*