7133: Update the build script help to include the installCore option

Reviewed-by: hirt

Author: oscerd

README.md

@@ -220,6 +220,7 @@ Prerequisites for building Mission Control:
 On Linux you can use the build.sh script to build JMC:
 ```
 usage: call ./build.sh with the following options:
+   --installCore to install the core artifacts
    --test        to run the tests
    --testUi      to run the tests including UI tests
    --packageJmc  to package JMC