Migrate BuildConfig to Gradle Build Files

Signed-off-by: Andy Scherzinger <info@andy-scherzinger.de>

app/build.gradle

@@ -126,6 +126,10 @@ android {
             }
         }
 
+        buildFeatures {
+            buildConfig = true
+        }
+
         productFlavors {
             // used for f-droid
             generic {

gradle.properties

@@ -4,7 +4,6 @@ NC_TEST_SERVER_USERNAME=test
 NC_TEST_SERVER_PASSWORD=test
 android.enableJetifier=true
 android.useAndroidX=true
-android.defaults.buildfeatures.buildconfig=true
 android.nonTransitiveRClass=false
 android.nonFinalResIds=false
 #android.debug.obsoleteApi=true