To configure Libav for iOS: ./configure --enable-cross-compile --arch=arm --target-os=darwin --cc='clang -arch armv7' --sysroot=$(xcrun --sdk iphoneos --show-sdk-path) --cpu=cortex-a8 --enable-pic If deploying to all generations, it's recommended to do separate out-of-tree builds for each architecture, then lipo together the resulting libs. For instance, assuming separate builds in armv6 and armv7: lipo -create -arch armv6 armv6/libavcodec/libavcodec.a -arch armv7 armv7/libavcodec/libavcodec.a -output universal/libavcodec.a and similar for each library. Then in XCode, make sure to build for both armv6 and armv7. If you only care about one generation (since the armv6 devices are too slow for instance), then lipo is unnecessary of course.
reddemonnet/gas-preprocessor
Perl script that implements a subset of the GNU as preprocessor that Apple's as doesn't
Perl