Original Source Modified By: Modding.MyMind XDA
ModdingMyMind AF

Tested with Busybox 1.23.1-Stericson (Recommended)

Built to be used on Arm devices.

Move the bash binary to /system/xbin. The rest must remain in the project folder.

Unpack Boot.img or Recovery.img:

root@android:/data/local/tmp/mkbootimg_tool/ARM # ./mkboot recovery_stock.img recoveryfolder

Unpack & decompress recovery_stock.img to recoveryfolder

****** WARNING ******* WARNING ******* WARNING ******                   

This image is built using NON-standard mkbootimg!                       
BASE is 0x001fff00
KERNEL_OFFSET is 0x00408100
RAMDISK_OFFSET is 0x00100100
SECOND_OFFSET is 0x00d00100

You can modify mkbootimg.c with the above value(s)                      

****** WARNING ******* WARNING ******* WARNING ******                   

  kernel         : zImage
  ramdisk        : ramdisk
  page size      : 2048
  kernel size    : 6597520
  ramdisk size   : 3141533
  base           : 0x001fff00
  kernel offset  : 0x00408100
  ramdisk offset : 0x00100100
  second_offset  : 0x00d00100
  tags offset    : 0x00000100
  cmd line       : vmalloc=384M mem=2044m@0x200000 psci=enable mmcparts=mmcblk0:p1(vrl),p2(vrl_backup),p7(modemnvm_factory),p18(splash),p22(dfx),p23(modemnvm_backup),p24(modemnvm_img),p25(modemnvm_system),p26(modem),p27(modem_dsp),p28(modem_om),p29(modemnvm_update),p30(3rdmodem),p31(3rdmodemnvm),p32(3rdmodemnvmbkp)

ramdisk is gzip format.
Unpack completed.

root@android:/data/local/tmp/mkbootimg_tools-master/ARM #

Repack Boot.img or Recovery.img:

root@android:/data/local/tmp/mkbootimg_tools-master # ./mkboot recoveryfolder recovery_stock.img
mkbootimg from recoveryfolder/img_info.
  kernel         : zImage
  ramdisk        : new_ramdisk.gz
  page size      : 2048
  kernel size    : 6597520
  ramdisk size   : 3142833
  base           : 0x001fff00
  kernel offset  : 0x00408100
  ramdisk offset : 0x00100100
  tags offset    : 0x00000100
  cmd line       : vmalloc=384M mem=2044m@0x200000 psci=enable mmcparts=mmcblk0:p1(vrl),p2(vrl_backup),p7(modemnvm_factory),p18(splash),p22(dfx),p23(modemnvm_backup),p24(modemnvm_img),p25(modemnvm_system),p26(modem),p27(modem_dsp),p28(modem_om),p29(modemnvm_update),p30(3rdmodem),p31(3rdmodemnvm),p32(3rdmodemnvmbkp)
Kernel size: 6597520, new ramdisk size: 3142833, recovery_stock.img: 9744384.
recovery_stock.img has been created.
...
root@android:/data/local/tmp/mkbootimg_tools-master #