builder: add an option for specifying build target

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
Upstream-commit: 33e07f41adc0ec96edad5f22bc2cfaec0d26ea58
Component: engine

components/engine/api/server/router/build/build_routes.go

@@ -56,6 +56,7 @@ func newImageBuildOptions(ctx context.Context, r *http.Request) (*types.ImageBui
 	options.ExtraHosts = r.Form["extrahosts"]
 	options.SecurityOpt = r.Form["securityopt"]
 	options.Squash = httputils.BoolValue(r, "squash")
+	options.Target = r.FormValue("target")
 
 	if r.Form.Get("shmsize") != "" {
 		shmSize, err := strconv.ParseInt(r.Form.Get("shmsize"), 10, 64)

components/engine/api/types/client.go

@@ -176,6 +176,7 @@ type ImageBuildOptions struct {
 	CacheFrom   []string
 	SecurityOpt []string
 	ExtraHosts  []string // List of extra hosts
+	Target      string
 }
 
 // ImageBuildResponse holds information