Issue 5920 - Remove the requirement for specifying --with-adjust-sdk-keyfile in mozconfig

mobile/android/moz.configure

Index: mobile/android/moz.configure
===================================================================
--- a/mobile/android/moz.configure
+++ b/mobile/android/moz.configure
@@ -141,18 +141,19 @@ include('gradle.configure')
 def check_install_tracking(install_tracking,
                            native_devices,
                            adjust_sdk_keyfile):
     if install_tracking:
         if not native_devices:
             die('You must specify MOZ_NATIVE_DEVICES=1 when'
                 ' building with MOZ_INSTALL_TRACKING=1')
         if not adjust_sdk_keyfile:
-            die('You must specify --with-adjust-sdk-keyfile=/path/to/keyfile when'
-                ' building with MOZ_INSTALL_TRACKING=1')
+            # Using default if Adjust SDK keyfile is not specified
+            # See https://issues.adblockplus.org/ticket/5920
+            adjust_sdk_keyfile = "$topsrcdir/mobile/android/base/adjust-sdk-sandbox.token"
 
 # Must come after the ../../toolkit/moz.configure.
 @depends('MOZ_ANDROID_MMA',
          'MOZ_NATIVE_DEVICES',
          'MOZ_ANDROID_GCM',
          '--with-leanplum-sdk-keyfile')
 def check_android_mma(android_mma,
                       native_devices,