[CMake] Specify the executable extension?

[alaterale at elitemail.org]

Hi,
At work we've got a build system set up which creates elf files that are
then objcopy'ed to a bin file, but the ADD_EXECUTABLE command always
starts with an ".exe" extension.  While renaming the .exe file as a post
build step works, someone pointed out that if it is moved to .whatever
then the next time around it does the rebuilding over again, and if its
copied it just wastes disk space (since its a large elf file currently)
for the old .exe file.  We are using a custom gcc compiler from nintendo
so its not exactly supposed to be a win32 program.
I see that there are variables for the library extensions and so forth,
so is it possible to make one for executable formats?  That way we could
just override it in our CMakeLists.txt file.  This doesn't seem like it
would be too hard to do right?
Thanks,
~~Jeremy