update_engine: Remove dependency on libupdate_engine from the client.

The update_engine_client is a very small DBus client that only
depends on a single utils:: function from the update_engine daemon
codebase. Because of this, it was forced to be linked against many
libraries that it didn't use.

This patch factors out this glib helper function to a new
glib_utils.{cc,h} file and includes only that in the
update_engine_client binary.

BUG=chromium:396440
TEST=FEATURES=test emerge-link update_engine

Change-Id: Icf8d8b3c6ebd22cdb39e6674fb3d9071071ec941
Reviewed-on: https://chromium-review.googlesource.com/209472
Reviewed-by: David Zeuthen <zeuthen@chromium.org>
Tested-by: Alex Deymo <deymo@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/update_attempter.cc b/update_attempter.cc
index e2e1201..bd086a8 100644
--- a/update_attempter.cc
+++ b/update_attempter.cc
@@ -8,8 +8,8 @@
 #include <memory>
 #include <set>
 #include <string>
-#include <vector>
 #include <utility>
+#include <vector>
 
 #include <base/file_util.h>
 #include <base/logging.h>
@@ -30,6 +30,7 @@
 #include "update_engine/dbus_wrapper_interface.h"
 #include "update_engine/download_action.h"
 #include "update_engine/filesystem_copier_action.h"
+#include "update_engine/glib_utils.h"
 #include "update_engine/hardware_interface.h"
 #include "update_engine/libcurl_http_fetcher.h"
 #include "update_engine/metrics.h"