添加rtthread相关代码

riscv/rtthread/components/libc/cplusplus/cxx_crt.h

@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2006-2021, RT-Thread Development Team
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+* Change Logs:
+* Date           Author       Notes
+* 2015-03-07     Bernard      Add copyright header.
+*/
+
+#ifndef CRT_H_
+#define CRT_H_
+
+#include <inttypes.h>
+#include <stdlib.h>
+
+void *operator new(size_t size);
+void *operator new[](size_t size);
+
+void operator delete(void * ptr);
+void operator delete[](void *ptr);
+
+extern "C" void __cxa_pure_virtual(void);
+extern "C" int  cplusplus_system_init(void);
+
+#endif