Use SystemCleaner on Android

We use Android's `SystemCleaner` when available, which should increase
overall GC performance.

See description here: https://developer.android.com/reference/android/system/SystemCleaner

scripts/uniffi_bindgen_generate_kotlin_android.sh

@@ -38,7 +38,7 @@ rustup target add x86_64-linux-android aarch64-linux-android armv7-linux-android
 CFLAGS="-D__ANDROID_MIN_SDK_VERSION__=21" AR=llvm-ar CARGO_TARGET_X86_64_LINUX_ANDROID_LINKER="x86_64-linux-android21-clang" CC="x86_64-linux-android21-clang" cargo build --profile release-smaller --features uniffi --target x86_64-linux-android || exit 1
 CFLAGS="-D__ANDROID_MIN_SDK_VERSION__=21" AR=llvm-ar CARGO_TARGET_ARMV7_LINUX_ANDROIDEABI_LINKER="armv7a-linux-androideabi21-clang" CC="armv7a-linux-androideabi21-clang" cargo build --profile release-smaller --features uniffi --target armv7-linux-androideabi || exit 1
 CFLAGS="-D__ANDROID_MIN_SDK_VERSION__=21" AR=llvm-ar CARGO_TARGET_AARCH64_LINUX_ANDROID_LINKER="aarch64-linux-android21-clang" CC="aarch64-linux-android21-clang" cargo build --profile release-smaller --features uniffi --target aarch64-linux-android || exit 1
-$UNIFFI_BINDGEN_BIN generate bindings/ldk_node.udl --language kotlin -o "$BINDINGS_DIR"/"$PROJECT_DIR"/lib/src/main/kotlin || exit 1
+$UNIFFI_BINDGEN_BIN generate bindings/ldk_node.udl --language kotlin --config uniffi-android.toml -o "$BINDINGS_DIR"/"$PROJECT_DIR"/lib/src/main/kotlin || exit 1
 
 JNI_LIB_DIR="$BINDINGS_DIR"/"$PROJECT_DIR"/lib/src/main/jniLibs/ 
 mkdir -p $JNI_LIB_DIR/x86_64 || exit 1

uniffi-android.toml

@@ -0,0 +1,3 @@
+[bindings.kotlin]
+android = true
+android_cleaner = true