wildcard expansion in targets and in prerequisites.

as used in kati's Makefile

go_src_stamp: $(GO_SRCS) cmd/*/*.go

cmd/*/*.go should be expanded as wildcard.
for now, kati doesn't expand the wildcard, so fails as

**\* No rule to make target "cmd/*/*.go", needed by "go_src_stamp".

for ninja generator, we might not need to generate `build cmd/*/*.go: phony" (and remove cmd/*/*.go from build go_src_stamp) ?