[CMake] WXWIDGETS_ADD_RESOURCES cannot use a custom-command generated resource file

[Rodolfo Schulz de Lima]

In my setup, the xrc resource file is generated from another file 
(wxformbuilder format) by a custom command, which calls wxformbuilder to 
convert it to xrc. This one is input to WXWIDGETS_ADD_RESOURCES.

Since WXWIDGETS_ADD_RESOURCES tries to read from xrc BEFORE it is 
created by wxformbuilder, an error occurs. The resource is not created 
because cmake is informed about the dependency at the end of the macro 
(in add_custom_command that calls wxrc). If I comment out the big 
foreach loop where the resource file is read, everything works fine, 
albeit now we don't have the dependency information of the files 
associated with the resource.

I cannot come with a solution to this with current cmake support. 
Ideally the call of file(READ ...) should trigger the file generation if 
it doesn't exist or its dependencies were modified. Is it reasonable to 
do it this way?

Regards,
rod