/ is writable on mac... leading to lots of awkward msi droppings?

[Dan Kegel]

Quentin Paris informs me that the root directory is
user-writable on MacOSX (shudder), which means
our beloved z: mapping leads to lots of garbage
directories named e.g. /fd91216cc2ce81eb2ce16a058619
after running msi installers.

Is this something Wine's msi could avoid doing?