build: add get-ndk-version.sh script

This can be used for convenience rather than having to manually search
through build.gradle.kts.

android/scripts/get-ndk-version.sh

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+script_path="$(readlink -f -- "$0")"
+script_dir="$(dirname -- "$script_path")"
+build_script_path="$script_dir/../app/build.gradle.kts"
+
+awk -F '"' '/ndkVersion = / { print $2 }' "$build_script_path"
+