Avoid excessive buffering if run by CI.

Required by Google Play.

This is required for targetSdkVersion=30.

apksigner requires running zipalign first.

This script setup a dummy android native app folder and call ndk-gdb from it.

It needs a modification in ANDROID_NDK since ndk-gdb may attach to the wrong
pid, cf. comments in the script.

This debuggable flag should not be set with release builds. Generally, graddle
is taking care of that.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1379

Improves the changes made in 57687779 by
using AudioManager.ACTION_AUDIO_BECOMING_NOISY rather than listening for
wired headset unplug events or Bluetooth headset disconnect events. This
method is more flexible, allowing the feature to work on other types of
audio output device, as well as Bluetooth devices that don't set their
device class correctly. This change also has the benefit of being more
responsive, pausing the audio before it is rerouted to the built-in
speaker.

https://developer.android.com/guide/topics/media-apps/volume-and-earphones

This reverts commit 6ed4aff4.  The
Meson wrap is broken on non-x86, because it unconditionally includes
<cpuid.h> which is an x86 only header.

Let cmake know that we're cross-crompiling.

Fixes the error:

 IllegalStateException: Not allowed to start service Intent { cmp=org.musicpd/.Main (has extras) }: app is in background

Needed for `requestLegacyExternalStorage` (commit ca02fb77).

This is a workaround for the new scoped storage design in Android 11:

 https://developer.android.com/about/versions/11/privacy/storage

This needs a proper solution eventually, but this quick fix will do
until we change "targetSdkVersion" to 30.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1061

The Google overlords require me to change to 29 or else I can't upload
new releases to Google Play.

 https://developer.android.com/distribute/best-practices/develop/target-sdk