This fixes the last couple of instances of the interpreter not being
passed to the python the scripts which makes them fail on OSes where
shebangs are not honoured (i.e. Windows)
Technically, these operations belong in the ObjectiveC module, where NSObject
is defined. Keep them there. However, we need to build the mock ObjectiveC
overlay with `-disable-objc-attr-requires-foundation-module` now.
...and collapse StaticVar/ClassVar and StaticLet/ClassLet into
StaticProperty/ClassProperty.
"var" and "let" aren't great nouns to use in diagnostics to begin with,
especially alongside semantic terms like "instance method". Focus on
the type vs. non-type aspect instead with "property", which better
matches how people talk about member vars (and lets) anyway.
