Fix version handling in `cmd/cvetool/version.go`

[evgenyz]

• Annotated vs unannotated tags (add --tags?)
• git-export

[Mab879]

We could sign tags or something like that fix this as well.

[evgenyz]

It depend on the release procedure. GH Web-UI based process creates unannotated tags, AFAIK.

[evgenyz]

In any case, we need to amend the release process to bake in the released version into the binary.