Probably I'm missing something. Maybe there's a subset of C++ that doesn't rely on it - a decent amount of the standard template library is generated at compile time.

If the dependency isn't there, it'll be fine.

Do you think it'll be worth having a check box in the installer to get the full runtime? Bearing in mind that most won't need it and many won't be able to install it? I'm not sure it is, but you've got a better idea of which packages are popular and which ones need it.