internal/pkg: exclusive artifacts

This alleviates scheduler overhead when curing many artifacts.

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

internal/rosa/python.go

@@ -32,7 +32,7 @@ func (t Toolchain) newPython() pkg.Artifact {
 		// breaks on llvm
 		"test_dbm_gnu",
 	}
-	return t.New("python-"+version, []pkg.Artifact{
+	return t.New("python-"+version, false, []pkg.Artifact{
 		t.Load(Make),
 		t.Load(Zlib),
 		t.Load(Libffi),
@@ -69,7 +69,7 @@ func (t Toolchain) newSetuptools() pkg.Artifact {
 		version  = "80.10.1"
 		checksum = "p3rlwEmy1krcUH1KabprQz1TCYjJ8ZUjOQknQsWh3q-XEqLGEd3P4VrCc7ouHGXU"
 	)
-	return t.New("setuptools-"+version, []pkg.Artifact{
+	return t.New("setuptools-"+version, false, []pkg.Artifact{
 		t.Load(Python),
 	}, nil, nil, `
 pip3 install \