Why am I getting "string_view: No such file or directory"

Question

I am trying to build my project over a cmake file. And started to get:

fatal error: string_view: No such file or directory

For the line below:

// Your First C++ Program


#include <string_view>


int main() {
    std::cout << "Hello World!";
    return 0;
}

I looked up in the internet, in stackoverflow question it is stated that this occurs because of the GCC version:String_view question.

I updated my gcc version as:

gcc --version
gcc (Ubuntu 7.5.0-3ubuntu1~16.04) 7.5.0
Copyright (C) 2017 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

But the problem is still here. I also using C++ 17 as below Cmake line:

cmake_minimum_required(VERSION 3.0)

set(CMAKE_BUILD_TYPE Debug)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++17")

project (sample)

add_executable(
    main
    main.cpp
)


# Set include directories
include_directories(SYSTEM

)

# Set linked files
link_directories(

)

target_link_libraries(
    main )

What could be the problem? Why cannot I compile the code?