Install the latest version of Qt libraries.
The main pkg file in the dmg will guide you through the steps to getting Qt 5.11 Opensource Edition installed on your machine.
It is not necessary to install the entire application, as we are not developing the source code, just compiling it. The figure below shows the only components required here, everything else can be 'unticked'. This saves a considerable amount of disc space.
This version installs in under the user library by default and the whole application now appears to reside under User/Qt5.11.2.
This means that this new version of Qt has to be added to the PATH variable so that the build process can find the libraries it needs. We simply amended our script for release 5.11.2 and above to contain:
echo "Add path to Qt5.11.2 to 'PATH'"