Increase the optimization level in the Makefile

Makefile

@@ -63,9 +63,9 @@ endif
 endif
 
 ifeq ($(SGX_DEBUG), 1)
-        SGX_COMMON_FLAGS += -O0 -g
+        SGX_COMMON_FLAGS += -O3 -g
 else
-        SGX_COMMON_FLAGS += -O2
+        SGX_COMMON_FLAGS += -O3
 endif
 
 SGX_COMMON_FLAGS += -Wall -Wextra -Winit-self -Wpointer-arith -Wreturn-type \