I updated Xcode and I ran into a project error:
clang: error: linker command failed with exit code 1 (use -v to see invocation)
and
ld: file is universal (3 slices) but does not contain a(n) armv7s slice: /Users/joe/Desktop/AdMob/libGoogleAdMobAds.a for architecture armv7s
This worked fine in the older version of Xcode, but not now. I know it has something to do with the file named: libGoogleAdMobAds.a
Which is used for AdMob ads…
Here is a screenshot:

UPDATE:

Check that you are using the latest AdMob SDK for iOS as that error implies the library doesn’t have the iOS 6 added architecture (armv7s).