Don't unnecessarily sign iOS/tvOS cores/libraries

pkg/apple/code-sign-cores.sh

@@ -55,6 +55,9 @@ IFS="
 # Loop through all items.
 for ITEM in $ITEMS;
 do
+    if codesign --display -r- "${ITEM}" | grep -q "${CODE_SIGN_IDENTITY_FOR_ITEMS}" ; then
+        echo "Skipping '${ITEM}', already signed"
+    else
         echo "Signing '${ITEM}'"
         codesign --force --verbose --sign "${CODE_SIGN_IDENTITY_FOR_ITEMS}" "${ITEM}"
         RESULT=$?
@@ -63,6 +66,7 @@ do
             IFS=$SAVED_IFS
             exit 1
         fi
+    fi
 done
 
 # Restore $IFS.