container driver: copy ca and user tls registries certs

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>

util/confutil/config.go

@@ -0,0 +1,25 @@
+package confutil
+
+import (
+	"os"
+
+	"github.com/pelletier/go-toml"
+	"github.com/pkg/errors"
+)
+
+// loadConfigTree loads BuildKit config toml tree
+func loadConfigTree(fp string) (*toml.Tree, error) {
+	f, err := os.Open(fp)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return nil, nil
+		}
+		return nil, errors.Wrapf(err, "failed to load config from %s", fp)
+	}
+	defer f.Close()
+	t, err := toml.LoadReader(f)
+	if err != nil {
+		return t, errors.Wrap(err, "failed to parse config")
+	}
+	return t, nil
+}