How do I turn a "fat" library into a "non-fat" library?

I'm trying to remove a duplicate object from a library with armv6 and armv7 architectures, i.e.,

$ lipo -info libx.a Architectures in the fat file: libx.a are: armv6 armv7

As expected, "ar d" does not work directly so I used "lipo -extract" to split the library. However, the resulting libraries are still 'fat' architecture.

$ ar d libx-armv6.a offendingduplicate.o ar: libx-armv6.a is a fat file (use libtool(1) or lipo(1) and ar(1) on it) ar: libx-armv6.a: Inappropriate file type or format

$ lipo -info x-ar开发者_Python百科mv6.a Architectures in the fat file: libx.a are: armv6

How can I un-fattify the library? (You can imagine the sorts of links that come up when you search for 'remove lipo fat file' in Google. Help!!)

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I am not familiar with lipo, but from its man page, it looks like you should be able to do this:

lipo libx.a -thin armv6 -output libx-armv6.a
lipo libx.a -thin armv7 -output libx-armv7.a