Update README.md

Author: NikolasK-source

README.md

@@ -7,7 +7,7 @@ Modbus tcp client that stores its data (registers) in shared memory objects.
 git submodule init
 mkdir build
 cd build
-cmake .. -DCMAKE_CXX_COMPILER=$(which clang++)
+cmake .. -DCMAKE_CXX_COMPILER=$(which clang++) -DCMAKE_BUILD_TYPE=Release
 cmake -build . 
 ```
 
@@ -36,4 +36,4 @@ Modbus_TCP_client_shm [OPTION...]
 ## Libraries
 This application uses the following libraries:
 - cxxopts by jarro2783 (https://github.com/jarro2783/cxxopts)
-- libmodbus by Stéphane Raimbault (https://github.com/stephane/libmodbus)
+- libmodbus by Stéphane Raimbault (https://github.com/stephane/libmodbus)