Add wasm_runtime_get_wasi_exit_code (#1748)

Refer to https://github.com/bytecodealliance/wasm-micro-runtime/issues/1738

core/iwasm/include/wasm_export.h

@@ -450,6 +450,18 @@ wasm_runtime_is_wasi_mode(wasm_module_inst_t module_inst);
 WASM_RUNTIME_API_EXTERN wasm_function_inst_t
 wasm_runtime_lookup_wasi_start_function(wasm_module_inst_t module_inst);
 
+/**
+ * Get WASI exit code.
+ *
+ * After a WASI command completed its execution, an embedder can
+ * call this function to get its exit code. (that is, the value given
+ * to proc_exit.)
+ *
+ * @param module_inst the module instance
+ */
+WASM_RUNTIME_API_EXTERN uint32_t
+wasm_runtime_get_wasi_exit_code(wasm_module_inst_t module_inst);
+
 /**
  * Lookup an exported function in the WASM module instance.
  *