This fixes the following issue when configuring canmv230:master
with Ubuntu stock toolchain and cmake 3.22:
```
CMake Error at .../arch/risc-v/src/cmake/Toolchain.cmake:218 (if):
if given arguments:
"STREQUAL" "GNU_RVG"
Unknown arguments specified
```
Signed-off-by: Yanfeng Liu <yfliu2008@qq.com>