With Xcode 5.1 Apple has made $(ARCHS_STANDARD) include arm64. If your project does not support arm64 you can simply change the architecture build setting to $(ARCHS_STANDARD_32_BIT) and it will not build arm64.
However if you have a target dependency that uses $(ARCHS_STANDARD) it will build arm64 and you will get an error because your project is expecting symbols that are not arm64.
Is there a way to make your target dependency aware what you are building against so it will build the valid architecture?