title: How to use cmake to check if some libraries exists before build our sources?
body: <p>Usually, open source packages will have cmake to check if some headers or libraries exists or not, I wish my own project has this same functionality.</p>
  
  <p>So I wish to know if cmake provides some command to check if some ".so"/".a"/".h" files exists in the current linux system or not, if not cmake will give me some hint to install them?</p>
  
  <p>How does cmake support this?</p>