Fix ucontext_t on x86

src/unix/notbsd/linux/other/b32/x86.rs

@@ -212,6 +212,7 @@ s_no_extra_traits!{
         pub uc_mcontext: mcontext_t,
         pub uc_sigmask: ::sigset_t,
         __private: [u8; 112],
+        __ssp: [::c_ulonglong; 4],
     }
 }