C++ CMake not referencing function with .h properly - c++

Question

SOLUTION:
Just don't be a noob and run make in the same directory as cmake
Thanks for your answers!
I'm starting with C++ programming and I'm trying to understand how to properly reference a function with .h and .cpp file. I have following files:
\\func.h
#ifndef FUNC_H
#define FUNC_H
int charout(int a, char b);
#endif
\\func.cpp
#include <iostream>
#include "func.h"
using namespace std;
int charout(int a, char b)
{
cout << a;
cout << b;
return 0;
}
\\main.cpp
#include <iostream>
#include "func.h"
using namespace std;
int main ()
{
int a; char b;
cout << "insert an integer " << endl;
cin >> a;
cout << "insert a letter " << endl;
cin >> b;
charout(a,b);
return 0;
}
I am compiling using CMake (with func.h in folder 'include') with following structure:
# Declare the version of the CMake API for forward-compatibility
cmake_minimum_required(VERSION 2.8)
# Declare the name of the CMake Project
project(manual)
# Add the directory to search for header files
include_directories(include)
# Define an executable target
add_executable(main func.cpp main.cpp)
When I try to make main.cpp I am receiving an error:
make main g++ main.cpp -o main /tmp/cctlsXUG.o: In function
main': main.cpp:(.text+0x80): undefined reference tocharout(int,
char)' collect2: error: ld returned 1 exit status : recipe
for target 'main' failed make: *** [main] Error 1
Can you please take a look and let me know where am I doing a mistake?
I will appreciate your feedback. I'm really stuck with this. Cheers!
UPDATE:
OK I managed to compile it with g++ func.cpp main.cpp - o main when I was trying to compile the same code with gcc I got errors of sort undefined reference to std::cout'
I've found out that gcc does not give an access to std of C++. Can I somehow fix my CMake files to use g++ instead of gcc? The project I have to deliver is supposed to have a CMakeLists.txt included.
Finally the last question: why does CMake works fine with function declaration and main in the same file, but not when I split the function into header, cpp and main?