GNU make grouped targets (&:)

     # The StackOverflow answer also demonstrates a simpler solution 
(using the
     # new `&:` operator instead of `:`), available since the release of GNU
     # make 4.3 in January 2020.  Alas, at the time of this writing 
(February
     # 2022) this version is still too new to be universally available.

https://gitlab.com/lilypond/lilypond/-/blob/d4efa89f2600a71bc68a48ea84fd4f04eaa14734/Documentation/tex/GNUmakefile?plain=1#L31-L34

https://www.gnu.org/software/make/manual/html_node/Multiple-Targets.html

How will we know when it is reasonable to use `&:`?
-- 
Dan