continuous-integration/drone/pr Build is passingDetails
Some commands (`go generate`) only support taking `GOFLAGS` from the environment
but setting `GOFLAGS` environment variable is ineffectual because the variable
of the same name defined in the Makefile shadows it.
We also have a custom `EXTRA_GOFLAGS` variable but we only pass that to `go build`.
Let’s add `EXTRA_GOFLAGS` to the `GOFLAGS` variable in the Makefile to allow passing
custom flags to Go through `EXTRA_GOFLAGS` environment variable.
Jan Tojnar