Android: target SDK 28, remove absolute path (#10568)

Android version: an absolute path was replaced with a call to the Environment class. The target SDK of 29 was decremented to a target SDK of 28 to fix an incompatibility with an SDK change. Game now builds; however a desktop version must be built first so that build artifacts are present in /bin.

src/openrct2-android/app/build.gradle

@@ -7,7 +7,7 @@ android {
     defaultConfig {
         applicationId 'io.openrct2'
         minSdkVersion 19
-        targetSdkVersion 29
+        targetSdkVersion 28
 
         versionCode 2
         versionName '0.2.5'

src/openrct2-android/app/src/main/java/io/openrct2/MainActivity.java

@@ -11,6 +11,8 @@
 import androidx.core.app.ActivityCompat;
 import androidx.core.content.ContextCompat;
 import androidx.appcompat.app.AppCompatActivity;
+
+import android.os.Environment;
 import android.text.TextUtils;
 import android.util.DisplayMetrics;
 import android.util.Log;
@@ -159,7 +161,9 @@ private void startGame() {
     // When building, ensure OpenRCT2 assets are inside their own directory within the APK assets,
     // so that we do not attempt to copy files out of the standard Android asset folders - webkit, etc.
     private void copyAssets() {
-        File dataDir = new File("/sdcard/openrct2/");
+        File dataDir = new File(Environment.getExternalStorageDirectory().toString()
+            + File.separator + "openrct2" + File.separator);
+
         try {
             copyAsset(getAssets(), "openrct2", dataDir, "");
         } catch (IOException e) {