title: read input variable in makefile and set variable upon it`s name
body: <p>I have a makefile where I want to read module name from input and then make directory based on it`s name. here is my code:</p>
  
  <pre><code>build:  
      @read -p "Enter Module Name:" module;  
      module_dir=./modules/$$module  
      mkdir -p $$module_dir/build;  
  </code></pre>
  
  <p>But after setting <strong>module_dir</strong>, it contains only <strong>./modules/</strong> (with no module name concatenated).<br>
  What is wrong in my code?</p>
  
  <p>thanks for your answers</p>