Merge pull request #260 from xu-cheng/switchless

Fix switchless sample code
diff --git a/samplecode/switchless/app/src/main.rs b/samplecode/switchless/app/src/main.rs
index aa08f6a..4de1afd 100644
--- a/samplecode/switchless/app/src/main.rs
+++ b/samplecode/switchless/app/src/main.rs
@@ -15,6 +15,9 @@
 // specific language governing permissions and limitations
 // under the License..
 
+#![feature(link_args)]
+#![link_args = "-Wl,--whole-archive -lsgx_uswitchless -Wl,--no-whole-archive"]
+
 extern crate sgx_types;
 extern crate sgx_urts;
 use sgx_types::*;