Fix sample sgx-ra build error (#1544)

Author: wenyongh

samples/sgx-ra/CMakeLists.txt

@@ -71,7 +71,7 @@ execute_process (
 ################ wamr runtime ###################
 add_custom_target (
               iwasm ALL
-              DEPENDS vmlib_untrusted vmlib_untrusted
+              DEPENDS vmlib_untrusted vmlib_untrusted vmlib
               COMMAND make -C  ${SGX_PLATFORM_DIR}/enclave-sample SGX_MODE=HW SGX_DEBUG=1 VMLIB_BUILD_DIR=${CMAKE_BINARY_DIR}
               COMMAND ${CMAKE_COMMAND} -E copy ${SGX_PLATFORM_DIR}/enclave-sample/enclave.signed.so ${CMAKE_BINARY_DIR}
               COMMAND ${CMAKE_COMMAND} -E copy ${SGX_PLATFORM_DIR}/enclave-sample/iwasm ${CMAKE_BINARY_DIR}