Co-targets (i.e. a list of whitespace-separated words for the target), is a well-known feature of Make, which basically allows for a makefile to assemble "similar" targets (i.e. they share the same recipe and prerequisites) into a single rule.
So, I have a makefile, like:
define targets
foo
bar
baz
endef
$(targets) ::
@echo '$@'
Executing, I get:
/bin/sh: 1: Syntax error: Unterminated quoted string
makefile:8: recipe for target 'foo
bar
baz' failed
make: *** [foo
bar
baz] Error 2
Really?