try to use glibc-locales instead of locale-gen

shaves at least 10 minutes off the build time while only costing about
20 mib when installed (even less when compressed)

mkosi.conf.d/00-packages-core.conf

@@ -5,6 +5,7 @@
 Packages=archlinux-keyring
          base
          btrfs-progs
+         glibc-locales # instead of running locale-gen as part of our build we install a package that has all locales pre-generated
          kernel-modules-hook
          kmod
          linux

mkosi.prepare.d/10-locale-archive.sh.chroot

@@ -1,21 +0,0 @@
-#!/bin/bash
-
-# SPDX-License-Identifier: GPL-2.0-only OR GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
-# SPDX-FileCopyrightText: 2025 Harald Sitter <sitter@kde.org>
-
-set -ex
-
-if [ "$1" = "final" ]; then
-    # Generate all locales. Because /usr/lib is not writable in the target system we need to ship all locales pre-generated.
-    # Sucks. But oh well.
-    # We can at least limit to UTF-8 variants because nobody uses the rest and Qt doesn't even work with them.
-    grep UTF-8 /usr/share/i18n/SUPPORTED > /etc/locale.gen
-
-    # Also allow overriding the list by setting a LOCALE_GEN environment variable
-    # in mkosi.local.conf or command line parameters for local builds
-    if [ -n "$LOCALE_GEN" ]; then
-        echo "$LOCALE_GEN" > /etc/locale.gen
-    fi
-
-    locale-gen
-fi