lint: add nolintlint and fix violations

We should be able to detect nolint comments that point to linters that
are disabled (such as with the removed structcheck).

Signed-off-by: Justin Chadwell <me@jedevc.com>

commands/build.go

@@ -81,10 +81,7 @@ type commonOptions struct {
 	progress     string
 	pull         *bool
 
-	// golangci-lint#826
-	// nolint:structcheck
 	exportPush bool
-	// nolint:structcheck
 	exportLoad bool
 }