Flutter Engine Clang Version

[Qxyat]

I encounter a problem while debugging the engine：single-step debugging behaves abnormally.
When I take a look at assembly code，it is different between Flutter Clang and Xcode Clang.
For example，the assembly code for [FlutterEngine initWithName: project: allowHeadlessExecution]:
result.zip
It looks like that Flutter Clang has more assembly code，

I am confused now：

1. What is the difference between the Flutter Clang and Xcode Clang?

2.What is the role of redundant assembly code? Single-step debugging behaves normally when I
use the Xcode Clang.

flutter doctor
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel unknown, v1.12.13+hotfix.7, on Mac OS X 10.14.6 18G4032, locale
zh-Hans-CN)

[✓] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
[✓] Xcode - develop for iOS and macOS (Xcode 11.3.1)
[✓] Android Studio (version 3.5)
[✓] Connected device (1 available)

Local Engine:
./flutter/tools/gn --runtime-mode=release --unopt

Xcode Clang Version:
Apple clang version 11.0.0 (clang-1100.0.33.17)
Target: x86_64-apple-darwin18.7.0
Thread model: posix

[zzjjob]

Flutter 2.0.2

flutter buildtools clang :
Fuchsia clang version 12.0.0 (https://llvm.googlesource.com/a/llvm-project 1a497ae9b83653682d6d20f1ec131394e523375d)
Target: x86_64-apple-darwin20.5.0
Thread model: posix

xcode clang:
Apple clang version 12.0.5 (clang-1205.0.22.9)
Target: x86_64-apple-darwin20.5.0
Thread model: posix

After compiling into a static library, there will be an inconsistent version error:
Flutter.framework/Flutter(flutter_framework_source.FlutterEngine.o): 'Unknown attribute kind (70) (Producer: 'LLVM12.0.0git' Reader: 'LLVM APPLE_1_1205.0.22.9_0')', using libLTO version 'LLVM version 12.0.5, (clang-1205.0.22.9)'