deploy_chrome: Finesse --board requirements.

--board is only required for stripping, so it may be skipped if
--build-dir is not specified, --no-strip is specified, or --strip-bin
is specified.

BUG=chromium:823996
TEST=manual + unittests

Change-Id: If2e46b3bdcc7c9670cf556d1e967ee362cf01b90
Reviewed-on: https://chromium-review.googlesource.com/977042
Commit-Ready: Achuith Bhandarkar <achuith@chromium.org>
Tested-by: Achuith Bhandarkar <achuith@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/scripts/deploy_chrome.py b/scripts/deploy_chrome.py
index 00af63d..babd460 100644
--- a/scripts/deploy_chrome.py
+++ b/scripts/deploy_chrome.py
@@ -513,8 +513,9 @@
   if options.build_dir and any([options.gs_path, options.local_pkg_path]):
     parser.error('Cannot specify both --build_dir and '
                  '--gs-path/--local-pkg-patch')
-  if options.build_dir and not options.board:
-    parser.error('--board is required when --build-dir is specified.')
+  if (not options.board and options.build_dir and options.dostrip and
+      not options.strip_bin):
+    parser.error('--board is required for stripping.')
   if options.gs_path and options.local_pkg_path:
     parser.error('Cannot specify both --gs-path and --local-pkg-path')
   if not (options.staging_only or options.to):