Reland "unpack_bootimg: Create symlink as alternate vendor ramdisk names" am: a08985e112 am: fd6c83c7c4 am: 0de42bca0e

Original change: https://android-review.googlesource.com/c/platform/system/tools/mkbootimg/+/1669629

Change-Id: If0de166c0c5fab814f31ebe3ea1d953e53fe7f3f