[CMake] Redirect output from add_custom_target()

[Rolf Eike Beer]

Micha Renner wrote:
> I would try
> 
>         add_custom_target( ${doc_target_name}
>              DEPENDS ${generated_conf}
>              COMMAND ${doxygen_exe} ${generated_conf} 2 > filename
>              WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
>              COMMENT "Generating documentation using Doxygen"
>          )

This will just fail as > has no meaning to doxygen. The only reason 
this works for you when you try that command in a terminal is that your 
Bourne-like shell will interpret the "> filename" and not pass it to 
doxygen at all. When you call doxygen like this from any generated 
project file there will be no shell involved.

Eike