title: compile C code for iOS armv7+arm64 using clang xcode 9
body: <p>I'm trying to make one binary for both armv7 and arm64.
  I am using this command to compile a simple C file:</p>
  
  <pre><code>clang -arch arm64 hello.c -o hello -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk
  </code></pre>
  
  <p>How can I add armv7 to this command to support old devices like the iPad 4? Knowing that xCode 9 stop supporting armv7 in iOS 11?</p>