Build credential provider targets as part of official build.

This is needed to make sure that credential provider pdbs make it to the
chromium symbol server.

Bug: 901825
Change-Id: I23e116d0c7405c827fc3ed5385013a9e776644d2
Reviewed-on: https://chromium-review.googlesource.com/c/1315533Reviewed-by: Scott Graham <scottmg@chromium.org>
Reviewed-by: Michael Moss <mmoss@chromium.org>
Commit-Queue: Roger Tawa <rogerta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606985}

BUILD.gn

@@ -803,6 +803,7 @@ if (is_win) {
   group("chrome_official_builder_no_unittests") {
     deps = [
       "//chrome/common/win:eventlog_provider",
+      "//chrome/credential_provider",
       "//chrome/installer/gcapi",
       "//chrome/installer/mini_installer",
       "//cloud_print",