ota: Let devices specify their own recovery-from-boot.p installer

Some devices apply transformations to the installed images, making
the sha1 checksums fail (or, worse, generating invalid images). If
"/system/etc/recovery-transform.sh" exists, run that instead, passing
the expected sizes and checksums as arguments in the form of

recovery-transform.sh <recovery_size> <recovery_sha1> <boot_size> <boot_sha1>

A direct emulation of the standard patcher could look like this, transformations
should be added as needed.

----------------
RECSIZE=$1
RECSHA1=$2
BOOTSIZE=$3
BOOTSHA1=$4

dd if=/dev/block/platform/msm_sdcc.1/by-name/recovery of=$C/recovery.img
dd if=/dev/block/platform/msm_sdcc.1/by-name/boot of=$C/boot.img

if ! applypatch -c EMMC:$C/recovery.img:$RECSIZE:$RECSHA1; then
  log -t recovery "Installing new recovery image"
  applypatch -b /system/etc/recovery-resource.dat EMMC:$C/boot.img:$BOOTSIZE:$BOOTSHA1 EMMC:$C/recovery.img $RECSHA1 $RECSIZE $BOOTSHA1:/system/recovery-from-boot.p || exit 1
else
  log -t recovery "Recovery image already installed"
fi
----------------

Conflicts:
	tools/releasetools/ota_from_target_files

Change-Id: Ie601841ca1cdad6b8f3b16e593d2718a92e8ca09
diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index 3944af5..7196c48 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -1422,6 +1422,10 @@
     return
 
   sh = """#!/system/bin/sh
+if [ -f /system/etc/recovery-transform.sh ]; then
+  exec sh /system/etc/recovery-transform.sh %(recovery_size)d %(recovery_sha1)s %(boot_size)d %(boot_sha1)s
+fi
+
 if ! applypatch -c %(recovery_type)s:%(recovery_device)s:%(recovery_size)d:%(recovery_sha1)s; then
   applypatch %(bonus_args)s %(boot_type)s:%(boot_device)s:%(boot_size)d:%(boot_sha1)s %(recovery_type)s:%(recovery_device)s %(recovery_sha1)s %(recovery_size)d %(boot_sha1)s:/system/recovery-from-boot.p && log -t recovery "Installing new recovery image: succeeded" || log -t recovery "Installing new recovery image: failed"
 else