title: make file with source subdirectories
body: <p>My latest project is in C++ and I am using GNU Make.
  The project directory layout is as follows:</p>
  
  <pre><code>project
  |-src
    |-subdir1
    |-subdir2 (containing tests)
  |-doc
  |-bin
  </code></pre>
  
  <p>I would like to be able to call <code>make</code> in the top level directory (i.e. need a makefile in the project directory) to compile all sources in both "src" subdirectories and place the resulting binaries in the "bin" directory.  </p>
  
  <p>What would be the best approach to do this? It would also be great if I didn't have to add a make rule for every source file, but just had one for all .cc and .h files in the directories.</p>