Absolute paths in APP_INCLUDES are prepended with application directory

[danielpieczko]

XCommon CMake prepends all the specified source files and include directories with the cmake list directory. If you specify the full absolute path, eg. for an include directory outside the application directory, there will be an error because this absolute path will be prepended with the absolute path to the application directory as well. Maybe it would be possible to check if each item in the source and include lists was an absolute path, and only prepend the cmake list directory onto the relative paths.