Thank you for reminding me it! Awesome finding.

Worth noting, each recipe can have its very own SHELL[0] (e.g., ruby recipe, that uses ruby command with -e flag):

  ruby: .SHELLFLAGS := -e
  ruby: SHELL := ruby
  ruby:
   greeting = "labas"
   puts "#{greeting}, ruby!"

[0]: http://agdr.org/2020/05/14/Polyglot-Makefiles.html