Android release_0.77.6 tarball does not reproduce from documented GitLab CI recipe

Hi Blockstream team,

Following the suggestion from green_android issue [#297](https://github.com/Blockstream/green_android/issues/297), I tested the Android GDK release build directly in the GDK repo.

I am trying to reproduce the Android native library shipped in:

https://github.com/Blockstream/gdk/releases/download/release_0.77.6/gdk-release_0.77.6.tar.gz

Official tarball SHA256:

`e86f164b77e690472f4cbdaf552d76ca847db885ced4502a49b5b0dfc96c9b8c`

I used the public GitLab CI recipe from release_0.77.6.

**Source:**

release_0.77.6
fa2e267c511cc336aabc3350da56edfd4fa9b9a3

**Image:**

docker.io/blockstream/gdk-android-builder@sha256:e08f5a77cc5472c9539cd0a83ee376efffab02eff4e768eae2c16c243f587f1e

**Command:**

```
./tools/build.sh --ndk arm64-v8a --buildtype release --no-deps-rebuild --external-deps-dir /prebuild/android-arm64-v8a --parallel 16 --install gdk-android-jni
```

I ran this twice in fresh clones.

Both local builds produced the same result:

`b60ce8002dd7bb37d22809993a1e8a3a229a575f5e9c253b1a671fb84013bdf3` lib/arm64-v8a/libgreen_gdk_java.so

The official release tarball contains:

`13d4ba62e75bebc4f8a9a50e2770a20def0469b1c470d321baadcadd407f07e7` lib/arm64-v8a/libgreen_gdk_java.so

The files have the same size:

26521752 bytes

But they differ substantially:

cmp -l local official | wc -l
6188322

Build IDs also differ:

local: 4507fd08da6325fe9af180846ecc571ffb4d2638
official: 50217d48b9f66acb2ab9e448b047e1a0fa3c8edd

So the public recipe appears deterministic locally, but it does not reproduce the official release_0.77.6 Android GDK artifact.

## Question:

Was the official gdk-release_0.77.6.tar.gz built with this exact image digest and command?

If not, could you share the exact CI image/input that produced the published tarball?

This matters for Blockstream Green Android reproducibility because the app-layer build now reproduces, and the remaining blocking difference is `libgreen_gdk_java.so`.

This came from the Blockstream Green Android 5.5.1 WalletScrutiny verification:

https://walletscrutiny.com/mobile/com.greenaddress.greenbits_android_wallet/#verificationId=f61e6f43e7d4907fa94f3aa933f06ee7005e2e688435ec62d783550ed3dd34d3

For context, the F-Droid variant of Blockstream Green 5.5.1 is reproducible in our verification.

https://walletscrutiny.com/mobile/com.greenaddress.greenbits_android_wallet/#verificationId=18ea3b9ad35aec8dcebed8ed4dfe0463825219393895813bd6c3d8973ac03319

That build path compiles GDK from source and matches the official F-Droid APK.

So the issue appears specific to reproducing the prebuilt Android GDK release artifact used by the Play Store build, not to the Green Android application code in general.