go1.20+: Refuse to work if cgo is enabled

On go1.20+ it is no longer possible to directly copy a cgo-enabled
library into a docker container. For this reason, this commit adds a
flag to commands that automatically make them fail with an appropriate
message if cgo is enabled.

cmd/system_update.go

@@ -31,6 +31,7 @@ func (systemupdate) Description() wisski_distillery.Description {
 	return wisski_distillery.Description{
 		Requirements: cli.Requirements{
 			NeedsDistillery: true,
+			FailOnCgo:       true,
 		},
 		ParserConfig: parser.Config{
 			IncludeUnknown: true,