[CMake] CONFIGURE_FILE won't overwrite existing file?

[Christian Convey]

It looks to me like CONFIGURE_FILE is a no-op when the target file
already exists *and* has the exact same content that it would have if
CONFIGURE_FILE ran.

I'm basing me belief by looking running some experiments and looking
at timestamps.

But this isn't mentioned in the online docs for CONFIGURE_FILE.

Does anyone know if it works the way I describe?

- Chrsitian