This worked for me: adding to CoreOF.xcconfig
HEADER_OPENSSL = "$(OF_PATH)/libs/openssl/include"and adding it to the OF_CORE_HEADERS as below:
OF_CORE_HEADERS = $(HEADER_OF) $(HEADER_POCO) $(HEADER_FREETYPE) $(HEADER_FREETYPE2) $(HEADER_FMODEX) $(HEADER_GLEW) $(HEADER_FREEIMAGE) $(HEADER_TESS2) $(HEADER_CAIRO) $(HEADER_RTAUDIO) $(HEADER_GLFW) $(HEADER_OPENSSL)