MINOR: add missing slash to enable file path

gpio_setup.cc

 // Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // NOTE: this file is translated from gpio_setup.py
 //
 // A script to create symlinks to platform specific GPIO pins.
 //
 // This script creates a set of symlinks pointing at the sys fs files returning
 // the appropriate GPIO pin values. Each symlink is named to represent the
@@ skipping 39 matching lines @@
 #include <ctype.h>
 #include <getopt.h>
 #include <glob.h>
 
 #include <string>
 #include <vector>
 #include <map>
 
 #define GPIO_ROOT               "/sys/class/gpio"
 #define GPIO_DEVICE_ROOT        GPIO_ROOT "/gpiochip"
-#define GPIO_ENABLE_FILE        GPIO_ROOT "export"
+#define GPIO_ENABLE_FILE        GPIO_ROOT "/export"
 
 // Can be changed using --pci_address command line option.
 #define DEFAULT_GPIO_DEVICE_PCI_ADDRESS "0000:00:1f.0"
 
 // Can be changed using --acpi_root command line option.
 #define DEFAULT_ACPI_ROOT "/sys/bus/platform/devices/chromeos_acpi"
 
 // can be changed using --symlink_root command line option.
 #define DEFAULT_SYMLINK_ROOT "/home/gpio"
 
@@ skipping 384 matching lines @@
   if (optind != argc)
     usage_help_exit(1);
 
   GpioChip gpioc(cmd_line_options.pci_address);
   gpioc.Attach();
   CreateGpioSymlinks(
       ParseAcpiMappings(cmd_line_options.acpi_root),
       gpioc, cmd_line_options.symlink_root.c_str());
   return 0;
 }