[CMake] SET_SOURCE_FILES_PROPERTIES for extra include directories

[James Bigler]

Is is possible to add include directories for a particular source file?

Right now I do:

INCLUDE_DIRECTORIES(${Extra_Include_Dir})

But this puts the extra includes on all the files for the libraries in 
the CMakeLists.txt file.  What I want is to do something like:

   SET_SOURCE_FILES_PROPERTIES(MyFile.cc
                               PROPERTIES INCLUDE_DIRECTORIES 
${Extra_Include_Dir})

This doesn't work, but perhaps I could add something to COMPILE_FLAGS, 
but how do I do this in a build system portable way?

James