add modbus install instructions

build_and_install.sh

@@ -29,6 +29,11 @@ then
     help
 fi
 
+# Build and install instructions for modbus library:
+# ./configure --prefix=/common/usr/cscofe/silecs/modbus/3.1.7 --enable-static
+# make -j4
+# make install
+
 # List of silecs packages which can be released
 PACKAGES="silecs-codegen silecs-model snap7 silecs-communication-cpp silecs-diagnostic-cpp silecs-cli silecs-cli-client"