gh-101981: Update macOS workflow by corona10 · Pull Request #101991 · python/cpython

• multi line string needs to declare sperate variable for this: https://trstringer.com/github-actions-multiline-strings/

But the devguide recipe does not consist of multiple commands on multiple lines as in that link, i.e. it's not "in the form of an output from one step, and an input to another step". It's a single shell command that has been split across lines in the devguide for readability and it doesn't need to be. (The POSIX command language standard calls it a "simple command": "A simple command is a sequence of optional variable assignments and redirections, in any sequence, optionally followed by words and redirections, terminated by a control operator." There is no piping involved here.)