Very recent versions of GNU make support this syntax:
foo bar biz &: baz boz
echo $^ > foo
echo $^ > bar
echo $^ > biz
(See (make)Multiple Targets, subheading `Rules with Grouped Targets')
This use of & is nonoverlapping with everything we care about, so we
can just pass it straight through. Passing through &: means we pass
through &:: too.
Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>