Two minor changes to allow fixes in cmd/vet's printf checking.
1. Pass package import path in vet config, so that vet knows
whether it is, for example, vetting "fmt".
2. Add new, but undocumented and for now unsupported
flag -vettool to control which vet binary is invoked during go vet.
This lets the cmd/vet tests build and test a throwaway vet.exe
using cmd/go to ensure type checking information, all without
installing a potentially buggy cmd/vet.
For #22936.
Change-Id: I18df7c796ebc711361c847c63eb3ee17fb041ff7
Reviewed-on: https://go-review.googlesource.com/83837
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>