The compiler already depends on the state of the file system though, notably because it depends on the source code. In the above case, the xml is essentially just another source file that happens to not be in the same language.

An important difference is that the compiler doesn't know it's using that file ahead of time, which could have some unforeseen consequences, but I don't see anything immediately worrying about that fact since the compiler didn't know about the source either at it's own compile time.