[macho] emit LC_BUILD_VERSION load command for supported OSes and platforms
This change lets LLVM use the LC_BUILD_VERSION command when building for macOS 10.14, iOS 12, tvOS 12, and watchOS 5.
Additionally, this change ensures that new platforms like Apple Silicon macOS / Mac Catalyst,
and simulators running on Apple Silicon alway use LC_BUILD_VERSION with the OS version set to the
minimum supported OS version if the deployment target version is older.
Differential Revision: https://reviews.llvm.org/D82836