Is it really necessary to patch the `./configure` script? I would assume that setting

    export MACOSX_DEPLOYMENT_VERSION=10.9
    export FP_MACOSX_DEPLOYMENT_TARGET=10.9
    export MACOSX_DEPLOYMENT_SDK=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX${MACOSX_DEPLOYMENT_VERSION}.sdk

in the `preConfigure` hook -- i.e. before `./configure` is run -- would have the same effect?