With go 1.17 a change to the build flags was implemented:
https://go.googlesource.com/proposal/+/master/design/draft-gobuild.md
The formatter now automatically adds the forward-compatible build tag
format and the linter checks for them, so we need to include them in our
code.
We create a new build flag for running the bitcoind tests without the
txindex enabled. We don't want this to be the default so we use a
negated build flag.
