codecs: add native build scripts for libvpx/opus/speex + fix CMake includes

- scripts/build-native-codecs.sh: cross-compile libvpx, opus, speex for
  Android ABIs (arm64-v8a, armeabi-v7a, x86_64) using NDK clang with -fPIC
- scripts/android-ndk.sh: NDK root detection helper
- scripts/native-build-cache.sh: ccache detection helper
- scripts/init-third-party-submodules.sh: init codec submodules
- scripts/ensure-gradle-wrapper.sh: gradle wrapper sanity check
- scripts/adb-reconnect.sh: ADB device discovery helpers
- ndk/CMakeLists.txt: per-ABI include dirs for opus/ and speex_config_types.h

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/native-build-cache.sh

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+# ccache detection helpers for native codec builds. Source this file.
+
+androidcast_ccache_wanted() {
+  [[ "${ANDROIDCAST_CCACHE:-auto}" != "off" ]] && command -v ccache >/dev/null 2>&1
+}
+
+androidcast_ccache_setup() {
+  if androidcast_ccache_wanted; then
+    export CC="ccache ${CC:-clang}"
+    export CXX="ccache ${CXX:-clang++}"
+  fi
+}