Our utility is called sha256.

Index: makeself.sh
--- makeself.sh.orig
+++ makeself.sh
@@ -678,7 +678,7 @@ if test "$SHA256" = y; then
 	if test -x "$SHA_PATH"; then
 		shasum=`eval "$SHA_PATH -a 256" < "$tmpfile" | cut -b-64`
 	else
-		SHA_PATH=`exec <&- 2>&-; which sha256sum || command -v sha256sum || type sha256sum`
+		SHA_PATH=`exec <&- 2>&-; which sha256 || command -v sha256 || type sha256`
 		shasum=`eval "$SHA_PATH" < "$tmpfile" | cut -b-64`
 	fi
 	if test "$QUIET" = "n"; then