添加rtthread相关代码

riscv/rtthread/components/libc/cplusplus/Kconfig

@@ -0,0 +1,23 @@
+menuconfig RT_USING_CPLUSPLUS
+    bool "Enable C++ features"
+    default n
+
+if RT_USING_CPLUSPLUS
+
+    config RT_USING_CPLUSPLUS11
+        bool "Enable C++11 standard multi-threading feature support"
+        default n
+        select RT_USING_POSIX_FS
+        select RT_USING_POSIX_STDIO
+        select RT_USING_PTHREADS
+        select RT_USING_RTC
+
+    config RT_USING_CPP_WRAPPER
+        bool "Enable RT-Thread APIs C++ wrapper"
+        default n
+
+    config RT_USING_CPP_EXCEPTIONS
+        bool "Enable C++ exceptions (will increase overhead)"
+        default n
+
+endif