title: Error when trying to build for iPhone simulator on Xcode
body: <p>How can I fix the error mentioned below?</p>
  
  <pre><code>ld: warning: URGENT: building for iOS simulator, but linking in object file (/Users/amy/Desktop/amy/swift_proj/swift_proj/include/libcrypto_x86_64.a(asn1_lib.o)) built for OSX. Note: This will be an error in the future.
  </code></pre>
  
  <p>I assume that to run on iPhone simulator, we use arch type x86_64. Is that correct? The library I'm trying to link (libcrypto) is of arch type x86_64.</p>
  
  <p>I've shown my Xcode build settings below:</p>
  
  <pre><code>Architectures: Standard architectures
  Base SDK: Latest iOS (iOS 11.4)
  Build active architecture only: No
  Supported platforms: iOS
  Valid architectures: arm64
  </code></pre>
  
  <p>I'm a newbie.</p>