Call truncate through perl. The binary is not available, and we can't pack it in otatools in AOSP, have to use an alternative. Bug: 27880501 Test: Generate a payload for boot.img which is not multiple of 4KiB. (cherry picked from commit d0e9a893163bb6f70b2bb003cda238d7e1a532ed) Change-Id: I45998cacda2111ba434e6d5c899d348f5b0bc50a