In v2.9.1 --no-boot-hacks is enabled by default. Run it like this as an example:

cd ~

./OMX-Kernel-Build-Script-2.9.1.sh \
  --xanmod-7 \
  --tag 7.1.13-xanmod1 \
  --afdo-profile ~/afdo/xanmod-7.1.13-autofdo-heavy-1h.afdo \
  --propeller \
  --force-thinlto \
  --force-fetch \
  -y