use old nvmutil for now, in lbmk

i'm trying to make nvmutil work on openbsd. the new code
in lbutils is a bit buggy, likely somewhere in mkhtemp.
i'm still debugging it.

Signed-off-by: Leah Rowe <leah@libreboot.org>

util/nvmutil/nvmutil.c

@@ -0,0 +1,50 @@
+/* SPDX-License-Identifier: MIT
+ * Copyright (c) 2022-2026 Leah Rowe <leah@libreboot.org>
+ *
+ * This tool lets you modify Intel GbE NVM (Gigabit Ethernet
+ * Non-Volatile Memory) images, e.g. change the MAC address.
+ * These images configure your Intel Gigabit Ethernet adapter.
+ */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <stddef.h>
+#include <stdlib.h>
+
+#include "include/common.h"
+
+int
+main(int argc, char *argv[])
+{
+	struct xstate *x = xstatus(argc, argv);
+	struct commands *cmd = &x->cmd[x->i];
+	struct xfile *f = &x->f;
+
+	unsigned long c;
+
+	if (cmd->run == NULL)
+		err(errno, "Command not set");
+
+	cmd->run();
+
+	for (c = 0; c < items(x->cmd); c++)
+		x->cmd[c].run = cmd_helper_err;
+
+	if ((cmd->flags & O_ACCMODE) == O_RDWR)
+		write_to_gbe_bin();
+
+	if (exit_cleanup() == -1)
+		err(EIO, "%s: close", f->fname);
+
+	if (f->io_err_gbe_bin)
+		err(EIO, "%s: error writing final file");
+
+	if (f->tname != NULL)
+		free(f->tname);
+
+	return EXIT_SUCCESS;
+}