bug#46700: Update instructions for mac OS installation of emacs via homebrew

[Alan Third <alan@idiocy.org>]

On Fri, Feb 26, 2021 at 04:40:19PM +0200, Eli Zaretskii wrote:
> > Date: Sun, 21 Feb 2021 15:48:46 -0500
> > From: "Tyler Chambers" <tyler@iheartapis.com>
> > 
> > on the page:
> > https://www.gnu.org/software/emacs/download.html
> > 
> > brew cask install emacs
> > 
> > should be replaced with:
> > 
> > brew install --cask emacs
> > 
> > as the cask subcommand has been removed from homebrew, in favor of a --cask flag.
> > 
> > relevant commit removing the cask subcommand from the usage instructions on the official homebrew
> > github:
> > https://github.com/Homebrew/homebrew-cask/commit/1fb821a4a50f75c92afe1ded44ccc6709314461b#diff-58a825c70bccfbe691d7ddbddb133275f4f657de6aeb4a502fa9fce279f8bf8d
> 
> Alan, any comments?  Should this be changed, and if so, should we do
> it on the release branch?

We don't make any recommendations about installing via homebrew in the
Emacs repository. nextstep/INSTALL, for example, only discusses
compiling from source.

I believe this is purely in reference to the website. I don't have
any special insight into homebrew, but I see this:

    breton:/Users/alan>brew cask install emacs
    Updating Homebrew...
    [...]
    Error: Unknown command: cask

so I guess the requested change is correct.

I have no idea how to update the website myself.
-- 
Alan Third