[EDIT: this allows the build process to complete, but the library does not seem to be fully functional in use]
Good news! I found at least a partial solution in a different thread. I have successfully built and installed SFGUI on MacOS 10.14.2 (although I haven't given it a test run yet). The problem revolved around a CoreFoundation framework in the OS, and the solution (such as it is) is to comment out certain lines in the CMakeLists.txt file.
That is to say, you can use CMake to do "configure" and "generate" (I used Unix makefiles, not XCode projects, so this solution may only apply to this approach).
Then, (before using "make"), navigate to the main SFGUI folder and open the file "CMakeLists.txt".
Here:
elseif( APPLE )
108 #find_library( COREFOUNDATION_LIBRARY CoreFoundation )
109 #mark_as_advanced( COREFOUNDATION_LIBRARY )
111 #add_library( CoreFoundation SHARED IMPORTED )
112 #set_target_properties(
113 # CoreFoundation PROPERTIES
114 # IMPORTED_LOCATION "${COREFOUNDATION_LIBRARY}"
115 # INTERFACE_INCLUDE_DIRECTORIES "/System/Library/Frameworks/CoreFoundation.framework/Headers"
116 #)
118 #target_link_libraries( ${TARGET} PUBLIC CoreFoundation )
set( SHARE_PATH "${CMAKE_INSTALL_PREFIX}/share/SFGUI" )
set( LIB_PATH "lib" )
elseif( "${CMAKE_SYSTEM_NAME}" MATCHES "Linux" )
all of the hashtag comment symbols were added by me, and if you comment out those numbered lines, save the file, then you can open Terminal and go to the build folder and execute "make".
Mods, is this info worth posting somewhere prominent for all Mac users of SFGUI to be aware of?
Thanks!