Fix mmctl build for FreeBSD (#29112)

server/cmd/mmctl/commands/utils_unix.go

@@ -1,8 +1,8 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
 
-//go:build linux || darwin
-// +build linux darwin
+//go:build linux || darwin || freebsd
+// +build linux darwin freebsd
 
 package commands