internal/rosa: pass stage alongside state

This cleans up many function signatures.

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

internal/rosa/zlib.go

@@ -2,12 +2,12 @@ package rosa
 
 import "hakurei.app/internal/pkg"
 
-func (t Toolchain) newZlib(s *S) (pkg.Artifact, string) {
+func (t Toolchain) newZlib() (pkg.Artifact, string) {
 	const (
 		version  = "1.3.2"
 		checksum = "KHZrePe42vL2XvOUE3KlJkp1UgWhWkl0jjT_BOvFhuM4GzieEH9S7CioepOFVGYB"
 	)
-	return s.NewPackage(t, "zlib", version, newTar(
+	return t.NewPackage("zlib", version, newTar(
 		"https://www.zlib.net/fossils/zlib-"+version+".tar.gz",
 		checksum,
 		pkg.TarGzip,