Evan Yan's blog

From mozilla web page, you can easily find out how to build a mozilla application(like Firefox and Thunderbird) with the default locale en-US. But it's not so easy to get how to build a l10n version. Here it is.

1. you have to check out  mozilla/tools/l10n/l10n.mk besides mozilla/client.mk.

$ cvs -d:pserver:anonymous-AT-cvs-mirror.mozilla-DOT-org:/cvsroot co mozilla/client.mk mozilla/tools/l10n/l10n.mk

2. do l10n-checkout before checking out the real code.

$ make -f client.mk l10n-checkout MOZ_CO_PROJECT=browser

3. create l10n files, replacing ab-CD with your locale, like zh-CN.

$ make -f tools/l10n/l10n.mk create-ab-CD MOZ_CO_PROJECT=browser

4. add this line into your .mozconfig file.

mk_add_options MOZ_CO_LOCALES=ab-CD

Then, do what you like as normal building.

$ make -f client.mk checkout
$ make -f client.mk build

 More detail information available here.