Cmake ошибка 2

I am trying to compile a simple code using cmake and I getting an error. The code and cmake file are as below. The test.cpp is the main file in which i have directly included test1.cpp. I have also included my CMake file and the error that I am getting on performing make.

test.cpp

#ifndef _IOSTREAM_
#include<iostream>
#endif
#include"test1.cpp"
using namespace std;
int main()
{
printing("hello");
return 0;
}

test1.cpp

#ifndef _IOSTREAM_
#include<iostream>
#endif
#include<string>
using namespace std;
void printing(string s)
{
cout<<s<<endl;
return;
}

CMakeLists.txt

cmake_minimum_required(VERSION 2.6)
set(CMAKE_C_COMPILER "/usr/bin/clang")
set(CMAKE_CXX_COMPILER "/usr/bin/clang++")
project(test)
set(CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS} -std=c++11)
add_executable(test test.cpp test1.cpp)

Error

CMakeFiles/test.dir/test1.cpp.o: In function 
printing(std::__cxx11::basic_string<char, std::char_traits<char>, 
std::allocator<char> >):
/home/vatsal/Desktop/test/test1.cpp:(.text+0x0): multiple definition 
of printing(std::__cxx11::basic_string<char, std::char_traits<char>, 
std::allocator<char> >)
CMakeFiles/test.dir/test.cpp.o:/home/vatsal/Desktop/test/test.cpp: 
(.text+0x0): first defined here
clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
CMakeFiles/test.dir/build.make:98: recipe for target test failed
make[2]: *** [test] Error 1
CMakeFiles/Makefile2:67: recipe for target CMakeFiles/test.dir/all 
failed
make[1]: *** [CMakeFiles/test.dir/all] Error 2
Makefile:83: recipe for target all failed
make: *** [all] Error 2

$  brew info python
python: stable 3.6.4 (bottled), devel 3.7.0b2, HEAD
Interpreted, interactive, object-oriented programming language
https://www.python.org/
/usr/local/Cellar/python/3.6.4_2 (3,593 files, 56.2MB)
  Poured from bottle on 2018-02-27 at 20:01:11
/usr/local/Cellar/python/3.6.4_4 (4,615 files, 97.4MB)
  Poured from bottle on 2018-03-10 at 14:42:05
From: https://github.com/Homebrew/homebrew-core/blob/master/Formula/python.rb
==> Dependencies
Build: pkg-config ✔, sphinx-doc ✘
Required: gdbm ✔, openssl ✔, readline ✔, sqlite ✔, xz ✔
Optional: tcl-tk ✘
==> Options
--with-tcl-tk
	Use Homebrew's Tk instead of macOS Tk (has optional Cocoa and threads support)
--devel
	Install development version 3.7.0b2
--HEAD
	Install HEAD version
==> Caveats
Python has been installed as
  /usr/local/bin/python3

Unversioned symlinks `python`, `python-config`, `pip` etc. pointing to
`python3`, `python3-config`, `pip3` etc., respectively, have been installed into
  /usr/local/opt/python/libexec/bin

If you need Homebrew's Python 2.7 run
  brew install python@2

Pip, setuptools, and wheel have been installed. To update them run
  pip3 install --upgrade pip setuptools wheel

You can install Python packages with
  pip3 install <package>
They will install into the site-package directory
  /usr/local/lib/python3.6/site-packages

See: https://docs.brew.sh/Homebrew-and-Python

I am trying to install extra-cmake-modules from source, and then I get an error after executing make command:

Extension error:
Could not import extension ecm (exception: No module named 'sphinxcontrib')
make[2]: *** [docs/CMakeFiles/documentation.dir/build.make:62: docs/doc_format_html] Error 2
make[2]: Leaving directory '/home/masterpi/Documents/Extra-CMake-Modules/extra-cmake-modules/build'
make[1]: *** [CMakeFiles/Makefile2:217: docs/CMakeFiles/documentation.dir/all] Error 2
make[1]: Leaving directory '/home/masterpi/Documents/Extra-CMake-Modules/extra-cmake-modules/build'
make: *** [Makefile:163: all] Error 2

It seems that the problem is about module Sphinx, but I tried to uninstall and install it again via pip and the error still occurred. So what can I do to fix it?
Here are logs when I executed cmake -DCMAKE_INSTALL_PREFIX=/usr .. and make command:

$ cmake -DCMAKE_INSTALL_PREFIX=/usr ..
-- WARNING: skipping tests that require PyQt
-- The following features have been enabled:

 * BUILD_HTML_DOCS, Generate HTML documentation for installed modules.
 * BUILD_MAN_DOCS, Generate man page documentation for installed modules.
 * BUILD_TESTING, Build automated tests.

-- The following OPTIONAL packages have been found:

 * Sphinx (required version >= 1.2), Tool to generate documentation., <https://www.sphinx-doc.org/>
   Required to build documentation for Extra CMake Modules.
 * QCollectionGenerator, Qt help collection generator., <https://www.qt.io/>
   Required to build Extra CMake Modules documentation in Qt Help format.
 * Qt5LinguistTools, Qt5 linguist tools., <https://www.qt.io/>
   Required to run tests for the ECMPoQmTools module.
 * Qt5Core, Qt5 core library., <https://www.qt.io/>
   Required to run tests for the ECMQtDeclareLoggingCategory module, and for some tests of the KDEInstallDirs module.
 * Qt5Network (required version >= 5.14.2)
 * Qt5Qml (required version >= 5.14.2)
 * Qt5QmlModels (required version >= 5.14.2)
 * Qt5Gui (required version >= 5.14.2)
 * Qt5Quick, Qt5 Quick library., <https://www.qt.io/>
   Required to run tests for the ECMQMLModules module.

-- The following features have been disabled:

 * BUILD_QTHELP_DOCS, Generate QtHelp documentation for installed modules.

-- Configuring done
-- Generating done
-- Build files have been written to: /home/masterpi/Documents/Extra-CMake-Modules/extra-cmake-modules/build
$ make
make[1]: Entering directory '/home/masterpi/Documents/Extra-CMake-Modules/extra-cmake-modules/build'
make[2]: Entering directory '/home/masterpi/Documents/Extra-CMake-Modules/extra-cmake-modules/build'
make[2]: Leaving directory '/home/masterpi/Documents/Extra-CMake-Modules/extra-cmake-modules/build'
make[2]: Entering directory '/home/masterpi/Documents/Extra-CMake-Modules/extra-cmake-modules/build'
[ 50%] sphinx-build html: see /home/masterpi/Documents/Extra-CMake-Modules/extra-cmake-modules/build/docs/build-html.log
/usr/lib/python3.8/importlib/__init__.py:127: RemovedInSphinx40Warning: The alias 'sphinx.util.pycompat.htmlescape' is deprecated, use 'html.escape' instead. Check CHANGES for Sphinx API modifications.
  return _bootstrap._gcd_import(name[level:], package, level)

Extension error:
Could not import extension ecm (exception: No module named 'sphinxcontrib')
make[2]: *** [docs/CMakeFiles/documentation.dir/build.make:62: docs/doc_format_html] Error 2
make[2]: Leaving directory '/home/masterpi/Documents/Extra-CMake-Modules/extra-cmake-modules/build'
make[1]: *** [CMakeFiles/Makefile2:217: docs/CMakeFiles/documentation.dir/all] Error 2
make[1]: Leaving directory '/home/masterpi/Documents/Extra-CMake-Modules/extra-cmake-modules/build'
make: *** [Makefile:163: all] Error 2