[CMake] Use of ADD_CUSTOM_COMMAND

[Gib Bogle]

I'm a real cmake novice, and I find the cmake documentation hard to follow, 
because it assumes that you know what you're doing (and I obviously don't) and 
doesn't provide examples.  I simply want to add to CMakeLists.txt an instruction 
to copy the executable created to another directory.  I gather that I want to 
use ADD_CUSTOM_COMMAND, and naively I thought this might do it:

ADD_CUSTOM_COMMAND( TARGET fubar POST_BUILD COMMAND copy fubar.exe 
somepath/fubar.exe)

but although this doesn't trigger a cmake error, it doesn't do anything either, 
and doesn't even seem to change Makefile.  Can someone point me in the right 
direction?  I'm using MinGW tools on Windows.

Thanks
Gib