deps: fix stripping of ffmpeg extension

Fix an issue where stripping of the FFMpeg extension would not occur,
as AGP would try to default to an entirely different NDK version.

Eventually I'm considering just vendoring the FFMpeg extension outright
once I can upstream some of the ExoPlayer patches.

app/build.gradle

@@ -10,6 +10,11 @@ plugins {
 
 android {
     compileSdk 33
+    // NDK is not used in Auxio explicitly (used in the ffmpeg extension), but we need to specify
+    // it here so that binary stripping will work.
+    // TODO: Eventually you might just want to start vendoring the FFMpeg extension so the
+    //  NDK use is unified
+    ndkVersion = "23.2.8568313"
     namespace "org.oxycblt.auxio"
 
     defaultConfig {