lacks some i18n locale definition file

Created by: haolian9

there is no full i18n definition files in image archlinux:20191205

reproduce:

there is a Dockerfile

FROM archlinux:20191205

# can be ignored, only for better net speed
RUN echo 'Server = http://mirrors.aliyun.com/archlinux/$repo/os/$arch' > /etc/pacman.d/mirrorlist

# the locale definition file I want not exists for sure
RUN [ ! -f /usr/share/i18n/locales/zh_CN ]

# so I try to get it by installing glibc
RUN pacman -Sy --noconfirm && pacman -S --noconfirm glibc

# and the file do exist in glibc package
RUN pacman -Ql glibc | grep -F '/usr/share/i18n/locales/zh_CN'

# but the file is still missing
RUN [ ! -f /usr/share/i18n/locales/zh_CN ]

RUN echo 'zh_CN.UTF-8 UTF-8' >> /etc/locale.gen

# it should be failed
RUN if locale-gen; then echo "passed!" && false; else echo "failed as expected"; fi

# lets get the file from `archlinux/base:latest`
COPY --from=archlinux/base:latest /usr/share/i18n/locales/zh_CN /usr/share/i18n/locales/zh_CN

# this time, it should be ok
RUN locale-gen

then with command docker build -t my/archlinux:latest .