Added: Export ANDROID__BUILD_VERSION_SDK in shell environment variable for the Android build SDK version

This is also required for `libtermux-exec-*-ld-preload.so` `$LD_PRELOAD` library as well for `termux-exec` version `>= 2.0.0`.

- https://github.com/termux/termux-exec-package/commit/db738a11

termux-shared/src/main/java/com/termux/shared/shell/command/environment/AndroidShellEnvironment.java

@@ -1,6 +1,7 @@
 package com.termux.shared.shell.command.environment;
 
 import android.content.Context;
+import android.os.Build;
 
 import androidx.annotation.NonNull;
 
@@ -20,6 +21,20 @@ import java.util.HashMap;
  */
 public class AndroidShellEnvironment extends UnixShellEnvironment {
 
+    /** Environment variable scope for Android. */
+    public static final String ANDROID_ENV_SCOPE = "ANDROID__"; // Default: "ANDROID__"
+
+    /**
+     * Environment variable for the Android build SDK version currently running on the device that
+     * is defined by {@link Build.VERSION#SDK_INT} and `ro.build.version.sdk` system property.
+     *
+     * - https://developer.android.com/reference/android/os/Build.VERSION#SDK_INT
+     * - https://developer.android.com/reference/android/os/Build.VERSION_CODES
+     *
+     * Default value: `ANDROID__BUILD_VERSION_SDK`
+     */
+    public static final String ENV_ANDROID__BUILD_VERSION_SDK = ANDROID_ENV_SCOPE + "BUILD_VERSION_SDK";
+
     protected ShellCommandShellEnvironment shellCommandShellEnvironment;
 
     public AndroidShellEnvironment() {
@@ -61,6 +76,8 @@ public class AndroidShellEnvironment extends UnixShellEnvironment {
         ShellEnvironmentUtils.putToEnvIfInSystemEnv(environment, "DEX2OATBOOTCLASSPATH");
         ShellEnvironmentUtils.putToEnvIfInSystemEnv(environment, "SYSTEMSERVERCLASSPATH");
 
+        ShellEnvironmentUtils.putToEnvIfSet(environment, ENV_ANDROID__BUILD_VERSION_SDK, String.valueOf(Build.VERSION.SDK_INT));
+
         return environment;
     }