internal/pkg: exclusive artifacts

This alleviates scheduler overhead when curing many artifacts.

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

internal/rosa/rosa.go

@@ -176,6 +176,7 @@ var absCureScript = fhs.AbsUsrBin.Append(".cure-script")
 // New returns a [pkg.Artifact] compiled on this toolchain.
 func (t Toolchain) New(
 	name string,
+	exclusive bool,
 	extra []pkg.Artifact,
 	checksum *pkg.Checksum,
 	env []string,
@@ -206,7 +207,7 @@ func (t Toolchain) New(
 		args[0] = "bash"
 		support = slices.Concat([]pkg.Artifact{
 			cureEtc{},
-			toolchainBusybox.New("stage3-"+version, nil, nil, nil, `
+			toolchainBusybox.New("stage3-"+version, false, nil, nil, nil, `
 tar -C /work -xf /usr/src/stage3.tar.xz
 rm -rf /work/dev/ /work/proc/
 ln -vs ../usr/bin /work/bin
@@ -258,7 +259,7 @@ ln -vs ../usr/bin /work/bin
 	}
 
 	return pkg.NewExec(
-		name, checksum, pkg.ExecTimeoutMax,
+		name, checksum, pkg.ExecTimeoutMax, exclusive,
 		fhs.AbsRoot, env,
 		path, args,
 
@@ -307,7 +308,7 @@ cat /usr/src/` + name + `-patches/* | \
 `
 		aname += "-patched"
 	}
-	return t.New(aname, stage3Concat(t, []pkg.Artifact{},
+	return t.New(aname, false, stage3Concat(t, []pkg.Artifact{},
 		t.Load(Patch),
 	), nil, nil, script, paths...)
 }