Document ProGuard retrace usage in BUILDING.md

Agent-Logs-Url: https://github.com/ArcaneChat/android/sessions/9b58d3e8-6163-4dac-8ca0-d6e7fa2df3a8

Co-authored-by: adbenitez <24558636+adbenitez@users.noreply.github.com>

BUILDING.md

@@ -243,3 +243,14 @@ $ANDROID_NDK_ROOT/ndk-stack --sym obj/local/armeabi-v7a --dump crash.txt > decod
 `obj/local/armeabi-v7a` is the extracted path from `deltachat-gplay-release-X.X.X.apk-symbols.zip` file from https://download.delta.chat/android/symbols/
 
 Replace `armeabi-v7a` by the correct architecture the logs come from (can be guessed by trial and error)
+
+### Deobfuscating Java/Kotlin Stack Traces
+
+Because the app uses code minification (ProGuard/R8), Java stack traces in crash reports are obfuscated.
+To decode them, use `retrace` with the `mapping.txt` file that is included in the symbols zip:
+
+```
+retrace mapping.txt crash.txt > decoded-crash.txt
+```
+
+`mapping.txt` is extracted from the same `deltachat-gplay-release-X.X.X.apk-symbols.zip` file available at https://download.delta.chat/android/symbols/

scripts/upload-release.sh

@@ -34,6 +34,7 @@ cd ../..
 SYMBOLS_ZIP="$APK-symbols.zip"
 rm $SYMBOLS_ZIP
 zip -r $SYMBOLS_ZIP obj
+zip $SYMBOLS_ZIP build/outputs/mapping/gplayRelease/mapping.txt
 ls -l $SYMBOLS_ZIP
 rsync --progress $SYMBOLS_ZIP jekyll@download.delta.chat:/var/www/html/download/android/symbols/