title: how do I build a binary for an earlier version of MacOS using CMake?
body: <p>I am using CMake to compile and link some command-line tools that I have written (in C). My development machine is MacOS 10.15 Catalina.</p>
  <p>I require the command-line tools to be able to run under MacOS High Sierra (10.13).</p>
  <p>What changes do I need to make to my build environment to be able to achieve this?</p>
  <p>At present, there is nothing in my CMakeLists that specifically targets Catalina, so I am unsure as to what I am doing wrong.</p>
  <p>I have a Mojave machine and I know that these tools will run under Mojave.</p>