[CMake] cmake / xcode / c++ header files

[g4 at novadsp.com]

How can I get the cmake xcode generator to add a /include folder to 
generated projects? The cmakelists contain these directives:

SET(${this_target}_HEADER_FILES ./a.h ./b.h)
SET_SOURCE_FILES_PROPERTIES(${this_target}_HEADER_FILES PROPERTIES 
HEADER_FILE_ONLY TRUE)
LIST(APPEND ${this_target}_SOURCE_FILES ${${this_target}_HEADER_FILES})

Thx++