Add gcp_installer.exe to archive config so that it can be signed.

Bug: 902890
Change-Id: I57021c1d018a48869aecf404854566bbf0b5dabd
Reviewed-on: https://chromium-review.googlesource.com/c/1330080Reviewed-by: Michael Moss <mmoss@chromium.org>
Commit-Queue: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607021}

chrome/tools/build/win/FILES.cfg

@@ -533,6 +533,12 @@ FILES = [
     'optional': ['dev', 'official'],
     'archive': 'chrome-win32-syms.zip',
   },
+  {
+    'filename': 'gcp_installer.exe',
+    'buildtype': ['official'],
+    'archive': 'gcp_installer.exe',
+    'filegroup': ['symsrc'],
+  },
   # Cloud Print files:
   {
     'filename': 'gcp_portmon.dll',