Re-enable AAR explosion if internal builds are enabled.

With AAR explosion disabled, builds are very likely to fail with Unity's
internal build system.  This patch re-enables AAR explosion on resolution
when the internal build system is used.

Fixes #100

Bug: 132070411
Change-Id: Ib2858910e3497c43eb9b1c9e06f7ec632227d8f0

Author: Stewart Miles

source/PlayServicesResolver/src/PlayServicesResolver.cs

@@ -1405,6 +1405,16 @@ private static void ResolveUnsafe(Action<bool> resolutionComplete = null,
 
             DeleteFiles(Resolver.OnBuildSettings());
 
+            // If the internal build system is being used and AAR explosion is disabled the build
+            // is going to fail so warn and enable explosion.
+            if (!AndroidBuildSystemSettings.Current.GradleBuildEnabled &&
+                !GooglePlayServices.SettingsDialog.ExplodeAars) {
+                Log("AAR explosion *must* be enabled when the internal build " +
+                    "system is selected, otherwise the build will very likely fail. " +
+                    "Enabling the 'explode AARs' setting.", level: LogLevel.Warning);
+                GooglePlayServices.SettingsDialog.ExplodeAars = true;
+            }
+
             xmlDependencies.ReadAll(logger);
 
             // If no dependencies are present, skip the resolution step.