title: unable to install g++ and build-essentials in ubuntu 20.04
body: <p>even after cleaning with <code>apt-get clean</code> it says there are broken packages. <code> sudo dpkg -l | grep ^..r</code> as mentioned in [1] returns nothing.</p>
  <pre><code>$ sudo apt-get install build-essential
  Reading package lists... Done
  Building dependency tree       
  Reading state information... Done
  Some packages could not be installed. This may mean that you have
  requested an impossible situation or if you are using the unstable
  distribution that some required packages have not yet been created
  or been moved out of Incoming.
  The following information may help to resolve the situation:
  
  The following packages have unmet dependencies:
   build-essential : Depends: libc6-dev but it is not going to be installed or
                              libc-dev
                     Depends: g++ (&gt;= 4:9.2) but it is not going to be installed
  E: Unable to correct problems, you have held broken packages.
  </code></pre>
  <p>[1] <a href="https://www.techbrown.com/fix-broken-packages-ubuntu-debian/" rel="noreferrer">https://www.techbrown.com/fix-broken-packages-ubuntu-debian/</a></p>