fix: use forward slashes in native library paths to fix BASS DllNotFoundException on Android

The AndroidNativeLibrary glob in osu.Android.props used backslash path
separators which silently match zero files on Linux CI runners, causing
libbass.so and other framework native .so files to be omitted from the APK.

Also adds:
- MSBuild error target to fail the build if libbass.so is missing
- APK verification step in release.yml to catch missing native libs

Agent-Logs-Url: https://github.com/winnerspiros/osu/sessions/1cb827b2-fc17-462a-b44c-cd932bcd649e

Co-authored-by: winnerspiros <1675249+winnerspiros@users.noreply.github.com>

Author: Copilot

.github/workflows/release.yml

@@ -215,6 +215,34 @@ jobs:
             exit 1
           fi
 
+      - name: Verify native libraries in APK
+        run: |
+          APK="${{ steps.find_apk.outputs.apk_path }}"
+          echo "Checking APK for required native libraries..."
+
+          NATIVE_LIBS=$(unzip -l "$APK" | grep "lib/arm64-v8a/.*\.so" || true)
+          echo "$NATIVE_LIBS"
+          echo ""
+
+          MISSING=0
+          for LIB in libbass.so libbass_fx.so libbassmix.so; do
+            if echo "$NATIVE_LIBS" | grep -q "$LIB"; then
+              echo "✅ $LIB found"
+            else
+              echo "::error::$LIB is MISSING from the APK — the app will crash at startup (DllNotFoundException)."
+              MISSING=1
+            fi
+          done
+
+          if [ "$MISSING" -ne 0 ]; then
+            echo ""
+            echo "::error::One or more required native libraries are missing. Check that the osu-framework submodule is initialised and the AndroidNativeLibrary glob in osu.Android.props resolves correctly."
+            exit 1
+          fi
+
+          echo ""
+          echo "All required native libraries present ✓"
+
       - name: Upload APK artifact
         uses: actions/upload-artifact@v7
         with:

osu.Android.props

@@ -85,17 +85,27 @@
 
   <ItemGroup>
     <!-- Use winnerspiros/osu-framework fork (net10.0-android, optimized) via submodule instead of ppy NuGet package -->
-    <ProjectReference Include="$(MSBuildThisFileDirectory)submodules\osu-framework\osu.Framework.Android\osu.Framework.Android.csproj" />
+    <ProjectReference Include="$(MSBuildThisFileDirectory)submodules/osu-framework/osu.Framework.Android/osu.Framework.Android.csproj" />
   </ItemGroup>
 
   <!-- Include framework native libraries (BASS audio, FFmpeg, etc.) from the submodule.
        When using a NuGet package these are bundled automatically; with a ProjectReference
        they must be declared explicitly or the app crashes at startup with
-       System.DllNotFoundException: bass (or similar). -->
+       System.DllNotFoundException: bass (or similar).
+       Use forward slashes — backslash globs silently match zero files on Linux CI runners,
+       which produces an APK without libbass.so (and the other native libs). -->
   <ItemGroup>
-    <AndroidNativeLibrary Include="$(MSBuildThisFileDirectory)submodules\osu-framework\osu.Framework.Android\arm64-v8a\*.so" Abi="arm64-v8a" />
+    <AndroidNativeLibrary Include="$(MSBuildThisFileDirectory)submodules/osu-framework/osu.Framework.Android/arm64-v8a/*.so" Abi="arm64-v8a" />
   </ItemGroup>
 
+  <!-- Fail the build early if libbass.so is missing.
+       A missing libbass.so means the app will crash on startup with DllNotFoundException.
+       This catches silent glob failures (e.g. uninitialised submodule, wrong path). -->
+  <Target Name="ValidateFrameworkNativeLibraries" BeforeTargets="Build">
+    <Error Condition="!Exists('$(MSBuildThisFileDirectory)submodules/osu-framework/osu.Framework.Android/arm64-v8a/libbass.so')"
+           Text="libbass.so not found in submodules/osu-framework/osu.Framework.Android/arm64-v8a/. Ensure the osu-framework submodule is initialised: git submodule update --init --recursive" />
+  </Target>
+
   <PropertyGroup>
     <!-- Fody does not handle Android build well, and warns when unchanged.
          Since Realm objects are not declared directly in Android projects, simply disable Fody. -->