[CMake] Overriding the toplevel directory name in a TGZ package?

[Clifford Yapp]

The CPack tool provides a variable CMAKE_INCLUDE_TOPLEVEL_DIRECTORY
option to control whether to set a toplevel directory in (say) a
tar.gz archive, but so far I have not been able to figure out if there
is a way to change this directory name to something not directly based
on the file name.  Trying to override CPACK_TOPLEVEL_DIRECTORY doesn't
seem to work.

Is there any way to get a tar.gz archive named (say)
NEW_PROJECT-3.1.1.tar.gz that unpacks into a toplevel directory simply
called PROJECT?

Thanks,
CY