weldr/composeTypesHandler: list image types per-arch

Currently all image types are supported on all arches, but in the
future we may want to restrict this. In that case, return the
image types that are valid for the arch in qusetion, rather than
all the possible ones.

Signed-off-by: Tom Gundersen <teg@jklm.no>

internal/weldr/api.go

@@ -1532,7 +1532,7 @@ func (api *API) composeTypesHandler(writer http.ResponseWriter, request *http.Re
 		Types []composeType `json:"types"`
 	}
 
-	for _, format := range api.distro.ListOutputFormats() {
+	for _, format := range api.arch.ListImageTypes() {
 		reply.Types = append(reply.Types, composeType{format, true})
 	}