[CMake] ADD_CUSTOM_COMMAND in different CMakeLists.txt

[Maik Beckmann]

Hello!

I' got a little problem which I like do describe. 

Given the structure...

Project_dir:
              - file: main_dummy.ccg
              - file: CMakeLists.txt
              -  dir: mydir

                 mydir: 
                        - file: CMakeLists.txt
----------------------------------------------------------


Where the contents are...

Project_dir/main_dummy:
<file>
int main()
{
    return 0;
}
</file>


Project_dir/CMakeLists.txt
<file>
project(myproject)

add_custom_command(
        OUTPUT ${PROJECT_SOURCE_DIR}/main.cc
        COMMAND ${CMAKE_COMMAND} -E copy
${PROJECT_SOURCE_DIR}/main_dummy.ccg
${PROJECT_SOURCE_DIR}/main.cc
        DEPENDS ${PROJECT_SOURCE_DIR}/main_dummy.ccg )

add_subdirectory(mydir)
</file>


Project_dir/mydir/CMakeLists.txt
<file>
add_executable(test ${PROJECT_SOURCE_DIR}/main.cc )
</file>
-------------------------------------------------------

I'm at Project_dir and creating a build directory
   mkdir build && cd build
and run
   cmake ../

This is what cmake says:
<output>
CMake Error: Cannot find source file
"/home/maik/Eigene-Dateien/Programmierung/C
++/Sandkasten/libgnomevfsmm-2.16.0/cmake-extensions/generate_files/main.cc" for target "test"

Tried extensions .c .C .c++ .cc .cpp .cxx .m .M .mm .h .h
++ .hm .hpp .hxx .in .txx
-- Configuring done
</output>

If I put the >>add_custom_command<< into
Project_dir/mydir/CMakeLists.txt everything works fine. Is this a
limitation of cmake?

Regards, Maik