VarDecls with `@_projectedValueProperty` have already had the property
wrapper transform applied. This only impacts swiftinterfaces, and if
a swiftinterface was produced against a Concurrency library that does
not declare `TaskLocal` as a macro, we need to ignore the macro to avoid
producing duplicate declarations. This is only needed temporarily until
all swiftinterfaces have been built against the Concurrency library
containing the new macro declaration.
