fix: ensure snapshot is valid (#48102)

* feat: add support for embedder snapshot validation

* fix: cpp lint

build/checksum_header.py

@@ -0,0 +1,37 @@
+#!/usr/bin/env python3
+
+import os
+import sys
+import hashlib
+
+dir_path = os.path.dirname(os.path.realpath(__file__))
+
+TEMPLATE_H = """
+#ifndef ELECTRON_SNAPSHOT_CHECKSUM_H_
+#define ELECTRON_SNAPSHOT_CHECKSUM_H_
+
+namespace electron::snapshot_checksum {
+
+const std::string kChecksum = "{checksum}";
+
+}  // namespace electron::snapshot_checksum
+
+#endif  // ELECTRON_SNAPSHOT_CHECKSUM_H_
+"""
+
+def calculate_sha256(filepath):
+    sha256_hash = hashlib.sha256()
+    with open(filepath, "rb") as f:
+        for byte_block in iter(lambda: f.read(4096), b""):
+            sha256_hash.update(byte_block)
+    return sha256_hash.hexdigest()
+
+input_file = sys.argv[1]
+output_file = sys.argv[2]
+
+checksum = calculate_sha256(input_file)
+
+checksum_h = TEMPLATE_H.replace("{checksum}", checksum)
+
+with open(output_file, 'w') as f:
+    f.write(checksum_h)