ERROR: unsatisfiable constraints: git (missing): required by: world[git]

1. 利用runner做前端依赖下载工作，runner放香港等海外机器，下载率相对较高
2. 需要npm yarn ssh git基础环境
3. 安装git时候报错如下

# 基础镜像node:12.18.0-alpine3.11

$ apk --no-cache add git
fetch http://dl-cdn.alpinelinux.org/alpine/v3.11/main/x86_64/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.11/community/x86_64/APKINDEX.tar.gz
WARNING: Ignoring http://dl-cdn.alpinelinux.org/alpine/v3.11/main/x86_64/APKINDEX.tar.gz: temporary error (try again later)
WARNING: Ignoring http://dl-cdn.alpinelinux.org/alpine/v3.11/community/x86_64/APKINDEX.tar.gz: temporary error (try again later)
ERROR: unsatisfiable constraints:
  git (missing
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