patcher: add patch_boot function

According to Magisk 25.0 release notes "Magisk no longer patches fstabs in most scenarios, which means AVB will remain intact; some custom kernels rely on AVB being stripped out for them by Magisk."
This means that a device like S9 will no longer boot stock fw after flashing just Magisk, so in order to ensure minimum compatibility we migrated the patches to multidisabler and added FBE disabler for ramdisk fstab for 8 and 9 flagship series for now, since neither no-verity-opt-encrypt can be flashed.

META-INF/com/google/android/update-binary

@@ -296,6 +296,67 @@ patch_libbluetooth() {
   fi
 }
 
+patch_boot() {
+	# Set up tools for boot.img patching
+	basedir=$(pwd)
+	unzip -o "$ZIPFILE" -d /tmp
+	chmod +x /tmp/tools/magiskboot
+	chmod +x /tmp/tools/busybox
+	magiskboot=/tmp/tools/magiskboot
+	busybox=/tmp/tools/busybox
+
+	boot=$($bb find /dev/block/platform -iname boot)
+	mkdir -p /tmp/bootimg && cd /tmp/bootimg
+    dd if=$boot of=/tmp/bootimg/old-boot.img bs=4096
+	$magiskboot unpack /tmp/bootimg/old-boot.img
+
+	# Boot.img patches - © topjohnwu - https://github.com/topjohnwu/Magisk/blob/master/scripts/boot_patch.sh
+	KEEPVERITY=false
+	KEEPFORCEENCRYPT=false
+	for dt in dtb kernel_dtb extra; do
+		[ -f $dt ] && $magiskboot dtb $dt patch && ui_print " - Patching fstab in $dt"
+	done
+
+	if [ -f kernel ]; then
+		ui_print " - Patching kernel for RKP/DEFEX/initramfs"
+		# Remove Samsung RKP
+		$magiskboot hexpatch kernel \
+		49010054011440B93FA00F71E9000054010840B93FA00F7189000054001840B91FA00F7188010054 \
+		A1020054011440B93FA00F7140020054010840B93FA00F71E0010054001840B91FA00F7181010054
+
+		# Remove Samsung defex
+		# Before: [mov w2, #-221]   (-__NR_execve)
+		# After:  [mov w2, #-32768]
+		$magiskboot hexpatch kernel 821B8012 E2FF8F12
+
+		# Force kernel to load rootfs
+		# skip_initramfs -> want_initramfs
+		$magiskboot hexpatch kernel \
+		736B69705F696E697472616D667300 \
+		77616E745F696E697472616D667300
+	fi
+
+	if [ -f ramdisk.cpio ]; then
+		$magiskboot cpio ramdisk.cpio extract
+		for i in fstab.*exynos* ; do
+			if [ -f $i ]; then
+				ui_print " -   Found $i, disabling encryption..."
+				md5=$( md5 $i )
+				# This comments out the offending line and adds an edited one.
+				sed -i -e 's/^\([^#].*\)fileencryption=[^,]*\(.*\)$/# &\n\1encryptable\2/g' $i
+				sed -i -e 's/^\([^#].*\)forceencrypt=[^,]*\(.*\)$/# &\n\1encryptable\2/g' $i
+
+				$magiskboot cpio ramdisk.cpio "add 0640 $i $i"
+				# file_changed $i $md5
+			fi
+		done
+	fi
+
+	$magiskboot repack old-boot.img
+	dd if=/tmp/bootimg/new-boot.img of=$boot bs=4096
+	cd $basedir
+}
+
 ui_print " "
 print_full_bar
 print_justified "Multi-disabler custom for Samsung devices"
@@ -364,6 +425,9 @@ fi
 
 vendor_free_size_check
 disable_fbe
+if echo $device | grep -E '[GN]9[56][05][FN]' >/dev/null; then
+	patch_boot
+fi
 disable_recovery_restoration
 
 if [ "$dp" != true ]; then