SGX target: fix docs build

Author: Jethro Beekman

src/libstd/sys/mod.rs

@@ -65,7 +65,7 @@ cfg_if! {
     if #[cfg(any(unix, target_os = "redox"))] {
         // On unix we'll document what's already available
         pub use self::ext as unix_ext;
-    } else if #[cfg(any(target_os = "cloudabi", target_arch = "wasm32"))] {
+    } else if #[cfg(any(target_os = "cloudabi", target_arch = "wasm32", target_env = "sgx"))] {
         // On CloudABI and wasm right now the module below doesn't compile
         // (missing things in `libc` which is empty) so just omit everything
         // with an empty module
@@ -86,7 +86,7 @@ cfg_if! {
         // On windows we'll just be documenting what's already available
         #[allow(missing_docs)]
         pub use self::ext as windows_ext;
-    } else if #[cfg(any(target_os = "cloudabi", target_arch = "wasm32"))] {
+    } else if #[cfg(any(target_os = "cloudabi", target_arch = "wasm32", target_env = "sgx"))] {
         // On CloudABI and wasm right now the shim below doesn't compile, so
         // just omit it
         #[unstable(issue = "0", feature = "std_internals")]