First install libgtk-3-dev and libgtkmm-3.0-dev then :
cmake_minimum_required(VERSION 3.7) project(project1) include(FindPkgConfig) pkg_check_modules(GTK REQUIRED "gtk+-3.0") include_directories(${GTK_INCLUDE_DIRS}) link_directories(${GTK3_LIBRARY_DIRS}) add_definitions(${GTK3_CFLAGS_OTHER}) set(CMAKE_CXX_STANDARD 11) set(SOURCE_FILES main.cpp) add_executable(untitled ${SOURCE_FILES}) target_link_libraries(${CMAKE_PROJECT_NAME} ${GTK3_LIBRARIES})
References :
http://stackoverflow.com/questions/27514291/how-to-add-compiler-arguments-using-cmake