title: Qt Creator, how do I add one c++ project to another?
body: <p>This seems like something that should be really simple, yet there doesn't seem to be a way to do it as one would expect. </p>
  
  <p>I have two separate c++ projects open in qt creator, and I would like to include/compile against one project in the other. </p>
  
  <p>Here's my layout:</p>
  
  <pre><code>project_a/
      project_a.pro
      someheaders.h
      somecode.cpp
      main.cpp
  
  project_b/
       project_b.pro
       someheaders.h
       somecode.cpp
       main.cpp
  </code></pre>
  
  <p>Basically I want to be able to include the files from project_a in project b. I have set project_a to be a dependency within project_b but that seems to have been wholly ineffectual as a means of using the two projects. What do I do? </p>