在MacOS Sierra 10.12上使用brew安装php7.4时出错

我正在尝试在MacOS Sierra上安装PHP7.4

brew install php@7.4

在警告说macOS 10.12不受支持后，我收到以下错误：

Error: An exception occurred within a child process:
  Errno::ENOENT: No such file or directory @ rb_sysopen - configure

brew医生

说：

Warning: Some installed kegs have no formulae!
This means they were either deleted or installed with `brew diy`.
You should find replacements for the following formulae:
  python@2

Warning: You have unlinked kegs in your Cellar.
Leaving kegs unlinked can lead to build-trouble and cause brews that depend on
those kegs to fail to run properly once built. Run `brew link` on these:
  python@2

Warning: You are using macOS 10.12.
We (and Apple) do not provide support for this old version.
You will encounter build failures with some formulae.
Please create pull requests instead of asking for help on Homebrew's GitHub,
Discourse, Twitter or IRC. You are responsible for resolving any issues you
experience while you are running this old version.

有没有办法解决这个问题？

需要解决的步骤

第一步，也是最重要的一步（除非你有很好的理由不这么做）：将macOS升级到适用于你的硬件的最新可用版本。看

运行

brew链接python@2

运行

brew安装php@7.4

---

由于与其他软件的兼容性问题，我无法升级我的系统。