Update README: clarify CUDA build option

README.md

@@ -69,11 +69,11 @@ cmake --build .
 ### CMake build options
 
 - `-DETHASHCL=ON` - enable OpenCL mining, `ON` by default,
-- `-DETHASHCUDA=OFF` - enable CUDA mining, `OFF` by default,
+- `-DETHASHCUDA=ON` - enable CUDA mining, `OFF` by default,
 - `-DETHSTRATUM=ON` - build with Stratum protocol support, `ON` by default.
 
 [CMake]: https://cmake.org
 [cpp-ethereum]: https://github.com/ethereum/cpp-ethereum
 [Genoil's fork]: https://github.com/Genoil/cpp-ethereum
 [Gitter]: https://gitter.im/ethereum-mining/ethminer
-[Hunter]: https://docs.hunter.sh
+[Hunter]: https://docs.hunter.sh