Update tools/cmake/README.md

Co-authored-by: Hugues Kamba <[email protected]>

Author: rajkan01

tools/cmake/README.md

@@ -92,7 +92,7 @@ $ mbedtools configure -t <TOOLCHAIN> -m <MBED_TARGET>
   ```
 * Run the following command to build the test binary with the baremetal profile
   ```
-  touch mbed-os.lib && mkdir build && cd build && cmake .. -G Ninja -DMBED_BAREMETAL_GREENTEA_TEST=ON && cmake --build .
+  touch mbed-os.lib && mkdir cmake_build && cd cmake_build && cmake .. -G Ninja -DMBED_BAREMETAL_GREENTEA_TEST=ON && cmake --build .
   ```
 
 Note: These steps will change when `mbedtools` implements a sub-command to invoke Greentea tests