wildcard expansion in targets and in prerequisites.

[Fumitoshi Ukai]

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) ?