build: pass down the cgroup manager to buildah

Pass down the cgroup manager to use to buildah.

Closes: containers#3938

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

cmd/podman/build.go

@@ -225,6 +225,14 @@ func buildCmd(c *cliconfig.BuildValues) error {
 	for _, arg := range c.RuntimeFlags {
 		runtimeFlags = append(runtimeFlags, "--"+arg)
 	}
+
+	conf, err := runtime.GetConfig()
+	if err != nil {
+		return err
+	}
+	if conf.CgroupManager == "systemd" {
+		runtimeFlags = append(runtimeFlags, "--systemd")
+	}
 	// end from buildah
 
 	defer runtime.DeferredShutdown(false)