It turns out there are valid usecases for exposing a standalone
objc-metaclass symbols and tbd files must encode it correctly.
resolves: rdar://118499886
TBD files contain a section reserved for obj-c classes. Previously,
TBDGen was adding symbols with this + normal globals with objc class
prefixes. This patch removes the extra globals being added.
This also accounts for this behavior for `validate-tbd-against-ir`
checking.
Resolves: rdar://101442087