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/libseccomp.go

@@ -12,6 +12,7 @@ func (t Toolchain) newLibseccomp() pkg.Artifact {
 	return t.New("libseccomp-"+version, false, []pkg.Artifact{
 		t.Load(Make),
 		t.Load(Bash),
+		t.Load(Coreutils),
 		t.Load(Gperf),
 
 		t.Load(KernelHeaders),