internal/rosa: replace busybox with toybox

The busybox artifact does not run on aarch64, and the workarounds required for it to compile successfully on x86_64 is unacceptably shaky. This change fully replaces it with toybox.

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

internal/rosa/libxml2.go

@@ -13,6 +13,7 @@ func (t Toolchain) newLibxml2() pkg.Artifact {
 	)
 	return t.New("libxml2-"+version, false, []pkg.Artifact{
 		t.Load(Make),
+		t.Load(XZ),
 	}, nil, nil, `
 cd /usr/src/
 tar xf libxml2.tar.xz