fixed not setting anything newer than c++11

cmake/enable_latest_cxx_support.cmake

@@ -26,7 +26,15 @@ CHECK_CXX_COMPILER_FLAG("-std=c++17" COMPILER_SUPPORTS_CXX17)
 CHECK_CXX_COMPILER_FLAG("-std=c++14" COMPILER_SUPPORTS_CXX14)
 CHECK_CXX_COMPILER_FLAG("-std=c++11" COMPILER_SUPPORTS_CXX11)
 CHECK_CXX_COMPILER_FLAG("-std=c++0x" COMPILER_SUPPORTS_CXX0X)
-if(COMPILER_SUPPORTS_CXX11)
+if(COMPILER_SUPPORTS_CXX17)
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++17")
+    set(${PROJECT_NAME}_CXX_FLAGS "${${PROJECT_NAME}_CXX_FLAGS} -std=c++17")
+    set(${PROJECT_NAME}_CMAKE_CXX_FLAGS "${${PROJECT_NAME}_CMAKE_CXX_FLAGS} -std=c++17")
+elseif(COMPILER_SUPPORTS_CXX14)
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14")
+    set(${PROJECT_NAME}_CXX_FLAGS "${${PROJECT_NAME}_CXX_FLAGS} -std=c++14")
+    set(${PROJECT_NAME}_CMAKE_CXX_FLAGS "${${PROJECT_NAME}_CMAKE_CXX_FLAGS} -std=c++14")
+elseif(COMPILER_SUPPORTS_CXX11)
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
     set(${PROJECT_NAME}_CXX_FLAGS "${${PROJECT_NAME}_CXX_FLAGS} -std=c++11")
     set(${PROJECT_NAME}_CMAKE_CXX_FLAGS "${${PROJECT_NAME}_CMAKE_CXX_FLAGS} -std=c++11")