pkg/build: don't call fetch_cvd for Android instances
pkg/build: don't call fetch_cvd for Android instances

Since the worker instances don't have network access, they won't be able
to download the Cuttlefish packages using this. Instead, we'll have to
pre-install the Cuttlefish tools in the GCE image.

xairy/syzkaller,google/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,xairy/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller