gki: Use shlex.split() to split command line argument strings am: d1d48f1edc am: 5ea2131098 am: 2dae9f75b8

Original change: https://android-review.googlesource.com/c/platform/system/tools/mkbootimg/+/2035983

Change-Id: I1c6ab66ed8d6e7aea5473df8d1600633d78bcc57