title: cmake and /opt/cmake/bin/cmake showing different version
body: <p>I am quite new to C++ programming and cmake. Kindly bear with me if the question seems simple.</p>
  <p>I am building an application for which cmake 3.9.0 is the minimum version required.</p>
  <pre><code>Setup.sh: Building rpclib with libc++.
  CMake Error at CMakeLists.txt:1 (cmake_minimum_required):
    CMake 3.9.0 or higher is required.  You are running version 3.5.1
  </code></pre>
  <p>So I planned to upgrade the cmake version and followed the below link.</p>
  <p><a href="https://geeksww.com/tutorials/operating_systems/linux/installation/downloading_compiling_and_installing_cmake_on_linux.php" rel="nofollow noreferrer">cmake_installation</a></p>
  <p>Note : Just to be clear, I don't want to purge the existing version as it might affect the <strong>ROS</strong> environment in my system.</p>
  <p>I have completed the installation and results given below.</p>
  <p>When I run <code>cmake -version</code>:</p>
  <pre><code>kk@kk-Lenovo-ideapad-320-15ISK:~/cmake-3.9.0$ cmake -version 
  cmake version 3.5.1
  
  CMake suite maintained and supported by Kitware (kitware.com/cmake).
  kk@kk-Lenovo-ideapad-320-15ISK:~/cmake-3.9.0$ 
  </code></pre>
  <p>And when I run <code>/opt/cmake/bin/cmake -version</code></p>
  <pre><code>kk@kk-Lenovo-ideapad-320-15ISK:~/cmake-3.9.0$ /opt/cmake/bin/cmake --version
  cmake version 3.9.0
  
  CMake suite maintained and supported by Kitware (kitware.com/cmake).
  kk@kk-Lenovo-ideapad-320-15ISK:~/cmake-3.9.0$
  </code></pre>
  <p>And issue/error with the application build remains the same as before.</p>
  <p>Could you please help me to update cmake or fix this existing version issue.</p>
  <p>Thank you</p>
  <p>KK</p>