> I've definitely been using .PHONY on various Linux and MacOS computers long before 2017.
Me too, and I've also used Makes which didn't (on e.g. Irix). What I wanted to express had been that you can't even rely on `.PHONY` existing, much less many other features.
Both BSDs and Solaris provide gmake via official channels.
There is "make" for Windows too, but it's not as relevant - the windows commands are so different, it's unlikely you'll have a cross-platform file for Windows and BSD/Linux, unless you require user to install unix tools on Windows, in which case they will likely come with GNU make.
I think in most cases, using GNU make is the easiest way to provide compatibility with multiple OSes. There are certainly exception - if your daily driver is FreeBSD, use BSD make. But for Mac OS or Linux users, GNU make is a good default.
Me too, and I've also used Makes which didn't (on e.g. Irix). What I wanted to express had been that you can't even rely on `.PHONY` existing, much less many other features.