This enforces that iOS Flutter.framework builds include arm64, armv7,
and x86_64 (simulator) architectures. This change also eliminates the
previous --device-out-dir option, which has been replaced by
--arm64-out-dir.
This adds support for --armv7-out-dir and renames --device-out-dir to
--arm64-out-dir for clarity. It preserves --device-out-dir as a fallback
until the bot recipe has been updated to use --arm64-out-dir.
This patch makes the sdk_xcode_harness work the same way as
hello_services. The goal is to eventually make these the same, but this
is just a first step.
