The newer level introduces APIs with additional nullability
attribution. This causes issues as the attribution sometimes collides
with expectations. Unwrap more cases to appease the nullability
attributes. One problematic area of this change is the handling for
`Process.run()`. The posix spawn APIs are described as:

```
typedef struct __posix_spawnattr* posix_spawnattr_t;
int posix_spawnattr_init(posix_spawnattr_t _Nonnull * _Nonnull __attr);
```

As the inner `_Nonnull` appertains to `posix_spawnattr_t`, it expects a
non-null pointer to a non-null pointer. However, as
`struct __posix_spawnattr` is opaque, we cannot allocate space for it
and thus must be acceptable to take a pointer to null to permit the
allocation.

…d overlay module

This allows us to prevent the ambiguity for various STATX defines from linux/stat.h when building for Android, as those are defined in the Android platform module