title: Parallel make: set -j8 as the default option
body: <p>I can set number of threads for the build process using <code>-j</code> argument. For example, I have 4 cores +4 virtual. When I write: <code>make -j8</code> the speed increases 4 times.</p>
  
  <p>Is it possible to set that value as default? (For example, in Linux Gentoo, in config file, it's possible to set this default value).</p>
  
  <p>p.s. I have Arch Linux</p>