fix(android): avoid blocked statx probes on legacy ARM32 devices

Vendor the pinned Rustix package with an Android-only weak libc lookup so missing statx returns ENOSYS and uses the existing stat64 fallback. Add an isolated Android smoke test with a hidden symbol and a seccomp filter that kills raw statx probes.

Verified 177 workspace tests, host Clippy, and ARM64 Android sandbox smoke test. ARM32 cross-target Clippy passes with the existing needless_return warning in binary.rs exempted; physical Android 10 ARM32 validation remains required.

scripts/check_android_statx.sh

@@ -0,0 +1,44 @@
+#!/usr/bin/env bash
+# Exercise statx fallback without requiring an old Android system image.
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_DIR="$(dirname "$SCRIPT_DIR")"
+case "${1:-arm64-v8a}" in
+  arm64-v8a) target=aarch64-linux-android; compiler=aarch64-linux-android24-clang ;;
+  armeabi-v7a) target=armv7-linux-androideabi; compiler=armv7a-linux-androideabi24-clang ;;
+  *) echo "Usage: $0 [arm64-v8a|armeabi-v7a]" >&2; exit 2 ;;
+esac
+: "${ANDROID_NDK_HOME:?Set ANDROID_NDK_HOME}"
+case "$(uname -s)" in
+  Darwin) ndk_host=darwin-x86_64 ;;
+  Linux) ndk_host=linux-x86_64 ;;
+  *) exit 2 ;;
+esac
+ndk_bin="$ANDROID_NDK_HOME/toolchains/llvm/prebuilt/$ndk_host/bin"
+target_env="${target//-/_}"
+linker_env="$(printf '%s' "$target_env" | tr '[:lower:]' '[:upper:]')"
+export "CARGO_TARGET_${linker_env}_LINKER=$ndk_bin/$compiler"
+export "CC_${target_env}=$ndk_bin/$compiler"
+export "AR_${target_env}=$ndk_bin/llvm-ar"
+export "BINDGEN_EXTRA_CLANG_ARGS_${target_env}=--sysroot=$ANDROID_NDK_HOME/toolchains/llvm/prebuilt/$ndk_host/sysroot --target=${compiler%-clang}"
+export RUSTFLAGS="${RUSTFLAGS:-} -C link-arg=-Wl,-z,max-page-size=16384"
+
+cd "$PROJECT_DIR/rust_backend"
+cargo rustc --locked --release -p spotiflac-extensions --example android_statx_smoke \
+  --target "$target" -- -C link-arg=-Wl,--wrap=dlsym
+remote="/data/local/tmp/spotiflac-statx-smoke-$$"
+trap 'adb shell rm -f "$remote" >/dev/null 2>&1 || true' EXIT
+adb push "target/$target/release/examples/android_statx_smoke" "$remote"
+adb shell chmod 700 "$remote"
+adb shell "$remote"
+adb shell "$remote --legacy"
+set +e
+adb shell "$remote --probe-blocked-syscall"
+status=$?
+set -e
+if [[ "$status" != 159 ]]; then
+  echo "Expected SIGSYS (159) from the isolated filter probe, got $status" >&2
+  exit 1
+fi
+echo "Android statx compatibility smoke test passed."