internal/rosa: pass stage alongside state

This cleans up many function signatures.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/rosa/libev.go

@@ -2,12 +2,12 @@ package rosa
 
 import "hakurei.app/internal/pkg"
 
-func (t Toolchain) newLibev(s *S) (pkg.Artifact, string) {
+func (t Toolchain) newLibev() (pkg.Artifact, string) {
 	const (
 		version  = "4.33"
 		checksum = "774eSXV_4k8PySRprUDChbEwsw-kzjIFnJ3MpNOl5zDpamBRvC3BqPyRxvkwcL6_"
 	)
-	return s.NewPackage(t, "libev", version, newTar(
+	return t.NewPackage("libev", version, newTar(
 		"https://dist.schmorp.de/libev/Attic/libev-"+version+".tar.gz",
 		checksum,
 		pkg.TarGzip,