opt: add build wrap in build.py

build.py

@@ -8,6 +8,7 @@ import urllib.request
 import shutil
 import hashlib
 import argparse
+import sys
 
 windows = platform.platform().startswith('Windows')
 osx = platform.platform().startswith(
@@ -17,6 +18,14 @@ exe_path = 'target/release/' + hbb_name
 flutter_win_target_dir = 'flutter/build/windows/runner/Release/'
 skip_cargo = False
 
+def custom_os_system(cmd):
+    err = os._system(cmd)
+    if err != 0:
+        print(f"Error occured when executing: {cmd}. Exiting.")
+        sys.exit(-1)
+# replace prebuilt os.system
+os._system = os.system
+os.system = custom_os_system
 
 def get_version():
     with open("Cargo.toml", encoding="utf-8") as fh: