title: Including subprojects .pri in another folder
body: <p>I have qt project <code>proj1</code> which depends on another (<code>proj2</code>).</p>
  
  <p>Directory tree is like this:</p>
  
  <pre><code>common/
        `--/pr1/ 
              proj1.pri
              main.cpp
        `--/pr2/
              proj2.pri
              src1.cpp
              src2.cpp
  </code></pre>
  
  <p>proj1 includes proj2:</p>
  
  <pre><code>include(../proj2.pri)
  </code></pre>
  
  <p>while in proj2.pri sources are listed as they are in current (pr2) dir:</p>
  
  <pre><code>SOURCES += src1.cpp \ 
             src2.cpp 
  </code></pre>
  
  <p>So when I try to build <code>proj1</code> I'm getting such error:</p>
  
  <pre><code>make: *** No rule to make target `src1.cpp', needed by `src1.o'.  Stop.
  </code></pre>
  
  <p>Is there any correct way to include subproject's sources (I need to do so for debugging) with help of pri-files ?</p>