Include build_config in the component updater files where it is needed.

Whenever we use platform-dependent code, build_config.h must be included,
otherwise build configuration files are not defined correctly inside that
compilation unit.

R=waffles

Change-Id: I82f6e4a37d221bf165417e3fd088de40da24367f
Reviewed-on: https://chromium-review.googlesource.com/879123
Reviewed-by: Joshua Pawlicki <[email protected]>
Commit-Queue: Sorin Jianu <[email protected]>
Cr-Commit-Position: refs/heads/master@{#530922}
diff --git a/components/update_client/update_client_unittest.cc b/components/update_client/update_client_unittest.cc
index f0a6278..e3e8846 100644
--- a/components/update_client/update_client_unittest.cc
+++ b/components/update_client/update_client_unittest.cc
@@ -21,6 +21,7 @@
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/values.h"
 #include "base/version.h"
+#include "build/build_config.h"
 #include "components/prefs/testing_pref_service.h"
 #include "components/update_client/component_unpacker.h"
 #include "components/update_client/crx_update_item.h"