[Zucchini] Build zucchini.exe on Windows builds

This CL makes the new Zucchini patcher available (alongside
Courgette), for diff generation experiments on Chrome release infra.
Note that this does NOT ship Zucchini.

This change was originally part of
https://chromium-review.googlesource.com/916553

Bug: 729154
Change-Id: I110da42dfa1c3ba05785a545cdd99fa5613caeea
Reviewed-on: https://chromium-review.googlesource.com/937396Reviewed-by: Nico Weber <thakis@chromium.org>
Reviewed-by: Samuel Huang <huangs@chromium.org>
Commit-Queue: Calder Kitagawa <ckitagawa@google.com>
Cr-Commit-Position: refs/heads/master@{#539180}

BUILD.gn

@@ -565,6 +565,7 @@ group("gn_all") {
       "//chrome/install_static:install_static_unittests",
       "//chrome/installer/gcapi",
       "//chrome/installer/setup:setup_unittests",
+      "//chrome/installer/zucchini",
       "//chrome/tools/build/win/syzygy:chrome_dll_syzygy",
       "//chrome_elf:chrome_elf_import_unittests",
       "//chrome_elf:chrome_elf_unittests",
@@ -763,6 +764,7 @@ if (is_win) {
       "//chrome/common/win:eventlog_provider",
       "//chrome/installer/gcapi",
       "//chrome/installer/mini_installer",
+      "//chrome/installer/zucchini",
       "//cloud_print",
       "//cloud_print/virtual_driver/win/port_monitor:copy_gcp_portmon_binaries",
       "//components/policy:pack_policy_templates",