android: Update Gradle plugin and build scripts and dependencies

This also references the NDK via ndkVersion and replaces the custom
ndk-build tasks.  It also replaces the deprecated compileSdkVersion and
increases it because dependencies of updated dependencies require that.

targetSdkVersion is not yet updated because there might be some work
required for Android 14 compatibility.

src/frontends/android/app/build.gradle

@@ -1,39 +1,36 @@
 apply plugin: 'com.android.application'
 
 android {
-    compileSdkVersion 33
-
     namespace 'org.strongswan.android'
 
     defaultConfig {
         applicationId "org.strongswan.android"
+        compileSdk 34
         minSdkVersion 21
         targetSdkVersion 33
         versionCode 80
         versionName "2.4.2"
+
+        externalNativeBuild {
+            ndkBuild {
+                arguments '-j' + Runtime.runtime.availableProcessors()
+            }
+        }
     }
 
-    sourceSets.main {
-        jniLibs.srcDir 'src/main/libs'
+    ndkVersion "26.1.10909125"
+
+    externalNativeBuild {
+        ndkBuild {
+            path 'src/main/jni/Android.mk'
+        }
     }
 
-    task buildNative(type: Exec) {
-        workingDir 'src/main/jni'
-        commandLine "${android.ndkDirectory}/ndk-build", '-j', Runtime.runtime.availableProcessors()
+    tasks.withType(JavaCompile).configureEach {
+        compileTask ->
+            options.compilerArgs << "-Xlint:unchecked" << "-Xlint:deprecation"
     }
 
-    task cleanNative(type: Exec) {
-        workingDir 'src/main/jni'
-        commandLine "${android.ndkDirectory}/ndk-build", 'clean'
-    }
-
-    tasks.withType(JavaCompile) {
-        compileTask -> compileTask.dependsOn buildNative
-        options.compilerArgs << "-Xlint:unchecked" << "-Xlint:deprecation"
-    }
-
-    clean.dependsOn 'cleanNative'
-
     buildTypes {
         release {
             minifyEnabled false
@@ -47,10 +44,10 @@ android {
 }
 
 dependencies {
-    implementation 'androidx.appcompat:appcompat:1.4.2'
-    implementation 'androidx.preference:preference:1.2.0'
+    implementation 'androidx.appcompat:appcompat:1.6.1'
+    implementation 'androidx.preference:preference:1.2.1'
     implementation 'androidx.legacy:legacy-support-v4:1.0.0'
-    implementation 'com.google.android.material:material:1.6.1'
+    implementation 'com.google.android.material:material:1.10.0'
     testImplementation 'junit:junit:4.13.2'
     testImplementation 'org.mockito:mockito-core:3.11.2'
     testImplementation 'org.powermock:powermock-core:2.0.9'