firstly, the upcoming version of GNU Make will indeed support multiple outputs in non-pattern rules (pattern rules always supported this, but pattern rules, uhh, have their own problems), using &: instead of :, resolving a bug from 2004. don't you just love the solid pace of those old GNU projects.

secondly, working around this was never very hard, albeit ugly: pretend your rule builds just one of the targets and have the other products depend on that one and simply touch themselves up to its timestamp.