The `__proto__` property is a special use case. It can be defined as a
computed property in an object expression, or via `defineProperty`. If
it’s assigned via a non-computed property in an object expression or via
a regular property assignment, even computed, this sets the prototype of
the object instead. This makes the generated code potentially vulnerable
to prototype pollution.

If multiple properties are defined, we still use
`Object.defineProperties`. Else we now use `Object.defineProperty`.

This is only supported in environments where Float16Array is available.

This helps bundlers with tree shaking.