[Cmake] ADD_CUSTOM_COMMAND and make clean

[Neil Killeen]

Hello again

Should I expect

% make clean

to function for Makefiles generated via the ADD_CSUTOM_COMMAND

As an example, I see statements like

% make clean

/DATA/ELARA_3/mitk/Output/sun4sol/Documentation/Developers: building clean

it correctly decends into this and other subdirectories
but does not remove anything.  The Makefile looks promising
but falters at the last...

cheers
Neil