download_gki: Decompress the Image.lz4 before checking SHA

Because the boot.img is compressed as lz4, sometimes the strings call
used to check its SHA will be truncated. Make this more consistent by
decompressing it first.

Bug: 194513402
Signed-off-by: J. Avila <elavila@google.com>
Change-Id: I1187427ac25ae36b32db89e66cb4bcc5c67a2044
(cherry picked from commit 845fccc1)

download_gki.sh

@@ -66,7 +66,13 @@ for file in $(ls ./*.zip); do
 done
 
 if [ -f "${BOOT_IMG_NAME}" ]; then
-  SHA_FILE="${BOOT_IMG_NAME}"
+  UNPACKED_BOOT_DIR=${TEMP_DIR}/boot_img_unpacked/
+  ${CUR_DIR}/tools/mkbootimg/unpack_bootimg.py --boot_img ${BOOT_IMG_NAME} \
+            --out ${UNPACKED_BOOT_DIR}
+  exit_and_clean_if_error $? "Unable to unpack ${BOOT_IMG_NAME}"
+  mv ${UNPACKED_BOOT_DIR}/kernel ./Image.lz4
+  lz4 -d ./Image.lz4 ./Image
+  SHA_FILE="Image"
 elif [ -f "vmlinux" ]; then
   SHA_FILE="vmlinux"
 else
@@ -99,13 +105,10 @@ fi
 
 cd ${GKI_PREBUILTS_DIR}
 if [ -n "${BOOT_IMG_NAME}" -a -f "${BOOT_IMG_NAME}" ]; then
-  echo "Copied userdebug variant ${BOOT_IMG_NAME} to boot.img."
   mv ${BOOT_IMG_NAME} boot.img
-  echo "Unpacking userdebug boot.img and retrieving Image.lz4."
-  ${CUR_DIR}/tools/mkbootimg/unpack_bootimg.py --boot_img boot.img \
-            --out ${TEMP_DIR}/boot_img_unpacked/
-  exit_and_clean_if_error $? "Unable to unpack boot.img"
-  mv ${TEMP_DIR}/boot_img_unpacked/kernel ./Image.lz4
+  echo "Copied userdebug variant ${BOOT_IMG_NAME} to boot.img."
+  mv ${TEMP_DIR}/Image.lz4 ./
+  echo "Copied Image.lz4 unpacked from ${BOOT_IMG_NAME}."
 fi
 echo "Update the GKI binaries to ab/${GKI_BUILD}