/usr/src/linux-source-4.4.0/debian/scripts/sub-flavour is in linux-source-4.4.0 4.4.0-119.143.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 | #!/bin/bash
. debian/debian.env
echo "SUB_PROCESS $FROM => $TO"
export from_pkg="linux-image-$ABI_RELEASE-$FROM"
export to_pkg="linux-image-$ABI_RELEASE-$TO"
from_moddir="debian/$from_pkg/lib/modules/$ABI_RELEASE-$FROM"
to_moddir="debian/$to_pkg/lib/modules/$ABI_RELEASE-$FROM"
install -d "debian/$to_pkg/boot"
install -m644 debian/$from_pkg/boot/config-$ABI_RELEASE-$FROM \
	debian/$to_pkg/boot/
install -m600 debian/$from_pkg/boot/{vmlinuz,System.map}-$ABI_RELEASE-$FROM \
	debian/$to_pkg/boot/
#
# Print some warnings if there are files in the sub-flavours list
# that do not actually exist.
#
cat ${DEBIAN}/sub-flavours/$TO.list | while read line
do
(
	cd debian/$from_pkg/lib/modules/$ABI_RELEASE-$FROM/kernel;
	#
	# If its a wildcard, then check that there are files that match.
	#
	if echo "$line" | grep '\*' > /dev/null
	then
		if [ `eval find "$line" -name '*.ko' 2>/dev/null|wc -l` -lt 1 ]
		then
			echo SUB_INST Warning - No files in $line
		fi
	#
	# Else it should be a single file reference.
	#
	elif [ ! -f "$line" ]
	then
		echo SUB_INST Warning - could not find "$line"
	fi
)
done
cat ${DEBIAN}/sub-flavours/$TO.list | while read line; do
	(
	cd debian/$from_pkg/lib/modules/$ABI_RELEASE-$FROM/kernel;
	if echo "$line" | grep '\*' > /dev/null
	then
		eval find "$line" -name '*.ko' 2>/dev/null || true
	elif [ -f "$line" ]
	then
		echo "$line"
	fi
	);
done | while read mod; do
	echo "SUB_INST checking: $mod"
	fromdir="/lib/modules/$ABI_RELEASE-$FROM/"
	egrep "^($fromdir)?kernel/$mod:" \
		$from_moddir/modules.dep | sed -e "s|^$fromdir||" -e 's/://' -e 's/ /\n/g' | \
	while read m; do
		m="${fromdir}$m"
		test -f debian/$to_pkg/$m && continue
		echo "SUB_INST installing: $m"
		install -D -m644 debian/$from_pkg/$m \
			debian/$to_pkg/$m
	done
done
 |