Use more prebuilt build-tools

For acp, we've been using an old prebuilt in prebuilts/sdk, but it's not
part of the SDK. Instead, we'll use a prebuilt in the build-tools
repository.

For ijar, we've been using the host libstdc++ to workaround the lack of
libc++ on some unbundled branches. Instead, use a prebuilt that can use
libc++.

For ziptime, we've been disabling it on unbundled branches, due to the
lack of libc++. Instead, use a prebuilt version of ziptime that can use
the prebuilt libc++.

Change-Id: If80f845ea06f76e3fe6765964e77c864eaf303d0