Android: Update to Gradle Plugin v4.2.1

android/app/build.gradle

@@ -2,7 +2,7 @@ apply plugin: 'com.android.application'
 
 android {
     compileSdkVersion 29
-    buildToolsVersion "29.0.2"
+    buildToolsVersion "30.0.2"
     defaultConfig {
         applicationId "com.github.stenzek.duckstation"
         minSdkVersion 23
@@ -14,6 +14,10 @@ android {
         release {
             minifyEnabled false
             proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
+
+            ndk {
+                debugSymbolLevel "FULL"
+            }
         }
     }
 
@@ -38,6 +42,9 @@ android {
     sourceSets {
         main.assets.srcDirs += "../../data"
     }
+
+    // Blocked on R21 until CMake is updated to 3.19 or later.
+    ndkVersion '21.4.7075529'
 }
 
 dependencies {