pmb.chroot.root: set LANG=UTF-8 (MR 1996)

This makes apk use the pretty character for printing progress

pmb/chroot/root.py

@@ -53,6 +53,7 @@ def root(args, cmd, suffix="native", working_dir="/", output="log",
 
     # Merge env with defaults into env_all
     env_all = {"CHARSET": "UTF-8",
+               "LANG": "UTF-8",
                "HISTFILE": "~/.ash_history",
                "HOME": "/root",
                "PATH": pmb.config.chroot_path,