Fix startup error in Android with Qt 5.15.x.

This is a known bug(*) with Qt 5.15 that causes libraries to not be
found when android:extractNativeLibs is left to default to false.  It
is not clear why some other developers are not affected by this.
Maybe something in their environment makes it default to true.

(*)See https://bugreports.qt.io/browse/QTBUG-61072 for details.

android/AndroidManifest.xml.in

@@ -1,6 +1,6 @@
 <?xml version="1.0"?>
 <manifest package="org.mythtv.mythfrontend" xmlns:android="http://schemas.android.com/apk/res/android" android:versionName="1.0" android:versionCode="1" android:installLocation="auto">
-    <application android:hardwareAccelerated="true" android:name="org.qtproject.qt5.android.bindings.QtApplication" android:label="mythfrontend" android:icon="@drawable/ic_launcher" android:banner="@drawable/banner" android:debuggable="true" android:theme="@style/AppTheme" >
+    <application android:hardwareAccelerated="true" android:name="org.qtproject.qt5.android.bindings.QtApplication" android:label="mythfrontend" android:icon="@drawable/ic_launcher" android:banner="@drawable/banner" android:debuggable="true" android:theme="@style/AppTheme" android:extractNativeLibs="true" >
         <activity android:configChanges="orientation|uiMode|screenLayout|screenSize|smallestScreenSize|layoutDirection|locale|fontScale|keyboard|keyboardHidden|navigation" android:name="org.qtproject.qt5.android.bindings.QtActivity" android:label="mythfrontend" android:screenOrientation="landscape" android:launchMode="singleTop" android:noHistory="false">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN"/>