[CMake] Recommandation for macOS framework install rules

[Lucas Soltic]

Hello,

By default library install() command uses CMAKE_INSTALL_PREFIX (/usr/local by default) as a base for relative install paths. But when you define install rules for macOS frameworks, it doesn't make much sense to install them there. I'd rather expect something like /Library/Frameworks.

On the other side, if you have more things to install like a "readme" or documentation that should go into /usr/local/share, it doesn't make sense to have them installed in /Library/Frameworks. So you can't just change CMAKE_INSTALL_PREFIX to be /Library/Frameworks.

What do you recommend to keep installation rules simple (ie. remain relative) and yet support installation of both frameworks and other things?

Best regards,
Lucas