Update gen_pio_frmwk_manifest.py

Author: Jason2866

tools/gen_pio_frmwk_manifest.py

@@ -3,6 +3,7 @@
 import os
 import re
 import sys
+import datetime
 
 MANIFEST_DATA = {
     "name": "framework-arduinoespressif32",
@@ -48,7 +49,7 @@ def main(dst_dir, version_string, commit_hash):
         return -1
 
     manifest_file_path = os.path.join(dst_dir, "package.json")
-    build_date = $(date -I)
+    build_date = datetime.date.today()
     with open(manifest_file_path, "w", encoding="utf8") as fp:
         MANIFEST_DATA["version"] = f"{converted_version}+sha.{commit_hash}"
         MANIFEST_DATA["date"] = f"{build_date}"