title: Xcode4 Linking Problem. File was built for archive which is not the architecture being linked (arm6)
body: <p>Recently, I switched to Xcode4 and when I compile my project I got following error.</p>
  
  <pre><code>ld: warning: ignoring file /Users/myname/Library/Developer/Xcode/DerivedData/appname-hezrgyqimckztgbdlslkavphdclw/Build/Products/Debug-iphoneos/libTapkuLibrary.a, file was built for archive which is not the architecture being linked (armv6)
  Undefined symbols for architecture armv6:
    "_OBJC_CLASS_$_TKLoadingView", referenced from:
        objc-class-ref in RootViewController.o
  </code></pre>
  
  <p>I opened the TapkuLibrary and checked that it's Architectures set to 'Standard (armv6 armv7)'.</p>
  
  <p>What can I do to fix this problem?</p>