title: Adding Testflight SDK: missing required architecture arm64 in file libTestFlight.a
body: <p>I'm adding the Testflight SDK to my iOS project, but now I can't build the IPA for it.</p>
  
  <p>The error I have is</p>
  
  <pre><code> ld: warning: ignoring file     /Users/RM/Dropbox/SAM_iOS/mainApp/SAM/TestFlightSDK2/libTestFlight.a, missing required architecture arm64 in file /Users/RM/Dropbox/SAM_iOS/mainApp/SAM/TestFlightSDK2/libTestFlight.a (3 slices)
   Undefined symbols for architecture arm64:
   "_OBJC_CLASS_$_TestFlight", referenced from:
    objc-class-ref in AppDelegate.o
   ld: symbol(s) not found for architecture arm64
   clang: error: linker command failed with exit code 1 (use -v to see invocation)
  </code></pre>
  
  <p>I've followed (three times) the steps detailed <a href="https://testflightapp.com/sdk/ios/doc/2.0.2/" rel="nofollow">here</a>, but the error keeps appearing.
  Any help is appreciated!</p>