Add std::num::NonZeroI...
diff --git a/sgx_tstd/src/num.rs b/sgx_tstd/src/num.rs
index e95f8f2..78eabfb 100644
--- a/sgx_tstd/src/num.rs
+++ b/sgx_tstd/src/num.rs
@@ -41,3 +41,5 @@
     NonZeroU8, NonZeroU16, NonZeroU32,
     NonZeroU64, NonZeroU128, NonZeroUsize,
 };
+
+pub use core::num::{NonZeroI8, NonZeroI16, NonZeroI32, NonZeroI64, NonZeroI128, NonZeroIsize};