Add CPackProductbuild support for the hostArchitectures option in Distribution.xml
The Distribution XML file contains a line called
options. Current CMake choices are here.
<options allow-external-scripts="no" customize="allow" rootVolumeOnly="false"></options>
However when building for Apple Silicon / x86_64 universal we want to set a sub-option in there
arm64,x86_64. Referenced here (but not updated for Apple Silicon). Installers build with
arm64,x86_64 should not force Rosetta 2 installation on Apple Silicon macs.
man productbuild says that on 11.0 (Big Sur) the default is set to
arm64,x86_64 rather than Intel only and has other useful context.
Maybe we want the option to set it manually as arm64 installers will want
arm64 only, intel only will want
x86_64 and universal 2 will want