postinst-script checks deps and exit if not exists; can be -.disabled.

postinst.d/10-nvidia-drivers

@@ -1,3 +1,8 @@
 #!/usr/bin/env sh
+
+[ -e "$0.disabled" ] && exit 0
+which make >/dev/null 2>&1 || exit 0
+[ -d "/usr/src/nvidia-drivers" ] || exit 0
+
 echo Build NVIDIA module... >&2
 exec make -C /usr/src/nvidia-drivers SYSSRC="/lib/modules/$1/build" install

postinst.d/90-dracut

@@ -1,3 +1,7 @@
 #!/usr/bin/env sh
+
+[ -e "$0.disabled" ] && exit 0
+which dracut >/dev/null 2>&1 || exit 0
+
 echo "dracut..." >&2
 exec dracut --force --kver "$1"

postinst.d/zz-grub-mkconfig

@@ -1,3 +1,6 @@
 #!/usr/bin/env sh
-echo "grub-mkconfig..." >&2
+
+[ -e "$0.disabled" ] && exit 0
+which grub-mkconfig >/dev/null 2>&1 || exit 0
+
 exec grub-mkconfig -o /boot/grub/grub.cfg