Built-in classes like jet.Int and jet.Iterable are loaded from source
files by KotlinBuiltIns class. It makes no sense to create JetLightClass
instances for such classes, moreover, it causes runtime failures.
Now we check the location a file was loaded from before creating a light
class, and skip if it is a built-in.
We also assert this in teh actual generation of light class bodies, and
print out OS information if something fails, because our detection strategy
may depend on OS-specific behavior.
Andrey Breslav
7719df1002