Run across this issue after switching to R8 shrinker from proguard.

Android Gradle plugin 3.4

-dontobfuscate enabled for easier debugging
Logcat:
```
java.lang.IllegalAccessError: Method 'java.lang.String com.mapbox.core.MapboxService.baseUrl()' is inaccessible to class 'com.mapbox.api.directions.v5.DirectionsResponseFactory' (declaration of 'com.mapbox.api.directions.v5.DirectionsResponseFactory' appears in /data/app/com.mapbox.services.android.navigation.app-DeTpyD0zikNY9Pe-wE5e5g==/base.apk!classes2.dex)
at com.mapbox.api.directions.v5.DirectionsResponseFactory.generateRouteOptions(DirectionsResponseFactory.java:78)
at com.mapbox.api.directions.v5.DirectionsResponseFactory.generate(DirectionsResponseFactory.java:31)
at com.mapbox.api.directions.v5.MapboxDirections$1.onResponse(MapboxDirections.java:184)
at retrofit2.ExecutorCallAdapterFactory$ExecutorCallbackCall$1$1.run(ExecutorCallAdapterFactory.java:70)
at android.os.Handler.handleCallback(Handler.java:873)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6863)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:537)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
```
Bytecode with call resulting in crash:
com.mapbox.api.directions.v5.DirectionsResponseFactory
```
.line 78
invoke-virtual {v6}, Lcom/mapbox/core/MapboxService;->baseUrl()Ljava/lang/String;

move-result-object v6

invoke-virtual {v5, v6}, Lcom/mapbox/api/directions/v5/models/RouteOptions$Builder;->baseUrl(Ljava/lang/String;)Lcom/mapbox/api/directions/v5/models/RouteOptions$Builder;

iget-object v6, p0, Lcom/mapbox/api/directions/v5/DirectionsResponseFactory;->mapboxDirections:Lcom/mapbox/api/directions/v5/MapboxDirections;
```
Actual code and referenced class:
com.mapbox.api.directions.v5.MapboxDirections 75:
```
.baseUrl(mapboxDirections.baseUrl())
```
where mapboxDirections is instance of com.mapbox.api.directions.v5.MapboxDirections not MapboxService

Issue was spotted in app i am working on using third party sdk i reproduced it in sample from sdk provider with updated config to run R8 (it requires token to run but analysing APK which can be done without providing it shows the problem) : https://github.com/freszu/mapbox-navigation-android