tools/mkrelease: minor optimization

Reduce the size of terminating empty blocks when creating a TAR.

tools/mkrelease.sh

@@ -279,6 +279,8 @@ sevenzip_compress_cmd+=("${options[@]}" a "${output}" "-i@${filelist}")
 tar_compress_cmd=(
     "${TAR}" --create --no-recursion
     --numeric-owner --owner=0 --group=0
+    # Minimize size of terminating empty blocks (7KB → 1KB).
+    --record-size=512
     --verbatim-files-from --files-from="${filelist}"
 )
 case "${format}" in