title: Partial build of Qt6 from source
body: <p>I need to install Qt6 on Ubuntu 18. Since qt6 is not in the repositories (or is it?), I have to compile them from the source code. However, I do this on my VDS server, which is not very powerful (2 cores, 4GB of RAM), so I do not have enough power for standard Qt6 compilation (compilation crashes with errors like &quot;I do not have enough RAM&quot;). I wondered if it was possible to compile only the modules I needed for QtHttpServer (an extension for Qt6).
  I tried to find this information in the documentation, but couldn't find anything.</p>