Add Linux SGX support (#106)

core/shared-lib/platform/zephyr/bh_platform.h

@@ -78,6 +78,8 @@ typedef void* (*thread_start_routine_t)(void*);
 #define wa_malloc bh_malloc
 #define wa_free bh_free
 
+#define bh_printf printf
+
 /* Unit test framework is based on C++, where the declaration of
  snprintf is different.  */
 #ifndef __cplusplus