archive-tar: keep const in checksum calculation
archive-tar: keep const in checksum calculation

For correctness, don't needlessly drop the const qualifier when casting.

Signed-off-by: Rene Scharfe <5c721353370dda279bee7751cb8d3ff68ef77242@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git