DOWNLOAD_SOUNDFONT fails silently in presence of connectivity issues

During the build process, the MuseScore CMake infrastructure tries by default to download the MuseScore_General soundfont (now known as MS_Basic as of current 4.x development). You did the right thing here by making this behavior optional and enabled by default : it is usually what people want, but in some cases like airgapped build servers, it is good to be able to disable that and download the sound font manually instead.

But unfortunately, in both the latest 3.6.2 release and the current git master, the CMake error handling is not quite right, which means that this process can fail silently. This results in a build that seems to run successfully but does not have the correct soundfont built in.

The silent build failure happens because if the initial VERSION file download fails (SF_VERSION_DL_STATUS is not 0), the CMake script simply skips the rest of the download process. Instead, it should at least print an error message, and in my opinion abort the build configuration as well (as done when a build dependency is not found).