That was my immediate assumption too, but part of the compiler's output is going to be some kind of a runtime library. If that itself is GPL 3 and the code generated by the compiler statically links to it, then I'm pretty sure a case could be made that the compiler's output is a derivitive work. Kind of sneaky and non intuitive, though.

This is all way out of my area of expertise, so take it with a grain of salt.