[go] disable go vet by default

Invoking go vet appears to contribute a very significant portion of Go binary
build time, including a significant portion of overall build time, as it
repeats significant volumes of work vetting shared dependencies and so on.

Users can instead invoke `fx go --package <package-name> vet`, or specify
`go_vet_enabled=true` in their build arguments to get the information for
their own purposes.

Change-Id: I49dfa062b7bcf3738ea842a96bc497db8de46c95
2 files changed