title: Swift on Linux: how to specify compiler optimizations
body: <p>Several threads on stackoverflow (e.g. <a href="https://stackoverflow.com/questions/24101718/swift-performance-sorting-arrays">this one</a>) discuss the different optimization levels (<code>Onone</code>, <code>O</code>, <code>Ounchecked</code>...) when compiling Swift applications. </p>
  
  <p>However, those postings are related to the development on OSX. It seems that those optimizations can be set directly via Xcode or xcrun (<code>xcrun swift -O3</code>).</p>
  
  <p>I'm wondering how to switch the different optimization levels when using the Swift compiler directly on Linux (Ubuntu 15.10). Currently, I'm building the application just by invoking <code>swift build</code> as it is shown in the docs, but I found no way no change the optimization level.</p>