[CMake] add_custom_command as target

[Gonzalo Garramuño]

Cmake provides add_custom_target, but that creates a target that gets 
run either always (ALL) or manually by running make <target>.

Cmake also provides an add_custom_command that tracks file dependencies 
and gets run when a dependency changes.  However, add_custom_command 
assumes the files are always intermediate files (ie. not targets) and 
for the command to actually appear in the Makefile, the output of the 
command has to have been added to add_executable or similar.

Is there a way to create an add_custom_target that tracks dependencies? 
  Or an add_custom_command that will act as a target (without needlessly 
being added to add_executable, etc).

Basically, I'm trying to have a macro that compiles NVidia's .cg files 
to profile shaders and as such the shaders are targets that depend on 
the cg files.

-- 
Gonzalo Garramuño
ggarra at advancedsl.com.ar

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