internal/rosa: pass stage alongside state

This cleans up many function signatures.

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

internal/rosa/mksh.go

@@ -2,16 +2,16 @@ package rosa
 
 import "hakurei.app/internal/pkg"
 
-func (t Toolchain) newMksh(s *S) (pkg.Artifact, string) {
+func (t Toolchain) newMksh() (pkg.Artifact, string) {
 	const (
 		version  = "59c"
 		checksum = "0Zj-k4nXEu3IuJY4lvwD2OrC2t27GdZj8SPy4DoaeuBRH1padWb7oREpYgwY8JNq"
 	)
 	scriptTest := "./test.sh -C regress:no-ctty\n"
-	if s.opts&OptSkipCheck != 0 {
+	if t.opts&OptSkipCheck != 0 {
 		scriptTest = ""
 	}
-	return s.New(t, "mksh-"+version, 0, s.AppendPresets(t, nil,
+	return t.New("mksh-"+version, 0, t.Append(nil,
 		Perl,
 		Coreutils,
 	), nil, []string{