[CMake] SWIG and dependency scanning

[Hugh Sorby]

I am using SWIG with #include directives in the interface file. When I 
compile the project for the  first time everything works fine, but when 
I make modifications to the header file included by the interface file 
the generated cxx wrapper file is not re-generated.  But the generated 
cxx wrapper file is re-compiled, it has the same #include directive as 
the interface file, but it hasn't changed.

So my question is how can I get the interface file to have a dependency 
on the #include'd header file?

Thanks,
Hugh.