internal/rosa: remove global handles

These no longer serve any purpose.

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

internal/rosa/tamago.go

@@ -8,8 +8,8 @@ func (t Toolchain) newTamaGo() (pkg.Artifact, string) {
 		checksum = "-nH3MjAzDDLTeJ2hRKYJcJwo5-Ikci4zOHfB8j1vKn7zrF9TS6zYaoLi8qohGwAE"
 	)
 	return t.New("tamago-go"+version, 0, t.Append(nil,
-		Bash,
-		Go,
+		bash,
+		_go,
 	), nil, []string{
 		"CC=cc",
 		"GOCACHE=/tmp/gocache",