[openwrt/openwrt] build: fix generation of large .vdi images

[LEDE Commits]

chunkeey pushed a commit to openwrt/openwrt.git, branch openwrt-22.03:
https://git.openwrt.org/cc54e19b2052d1f003637132d834bb4a2f2562d5

commit cc54e19b2052d1f003637132d834bb4a2f2562d5
Author: Adones Pitogo <pitogo.adones at gmail.com>
AuthorDate: Tue Jul 11 13:31:50 2023 +0800

    build: fix generation of large .vdi images
    
    Instead of loading the whole image into the memory when generating the
    sha256 sum, we load the file in chunks and update the hash incrementally
    to avoid MemoryError in python. Also remove a stray empty line.
    
    Fixes: #13056
    Signed-off-by: Adones Pitogo <pitogo.adones at gmail.com>
    (mention empty line removal, adds Fixes from PR)
    Signed-off-by: Christian Lamparter <chunkeey at gmail.com>
    (cherry picked from commit bdb4b78210cfb6bc8a6cda62fc990dd45ec3054c)
---
 scripts/json_add_image_info.py | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/scripts/json_add_image_info.py b/scripts/json_add_image_info.py
index 9aa2a19e45..056f0ccb5c 100755
--- a/scripts/json_add_image_info.py
+++ b/scripts/json_add_image_info.py
@@ -13,7 +13,6 @@ if len(argv) != 2:
 json_path = Path(argv[1])
 file_path = Path(getenv("FILE_DIR")) / getenv("FILE_NAME")
 
-
 if not file_path.is_file():
     print("Skip JSON creation for non existing file", file_path)
     exit(0)
@@ -37,7 +36,14 @@ def get_titles():
 
 
 device_id = getenv("DEVICE_ID")
-hash_file = hashlib.sha256(file_path.read_bytes()).hexdigest()
+
+sha256_hash = hashlib.sha256()
+with open(str(file_path),"rb") as f:
+    # Read and update hash string value in blocks of 4K
+    for byte_block in iter(lambda: f.read(4096),b""):
+        sha256_hash.update(byte_block)
+
+hash_file = sha256_hash.hexdigest()
 
 if file_path.with_suffix(file_path.suffix + ".sha256sum").exists():
     hash_unsigned = (