Only download binutils in standalone build

This condition is most useful in non-standalone build AND the higher
level DEPS file recurses into Dawn via recursedeps.

Bug: dawn:437
Change-Id: Ib0aa8366a1a45a80a1dc11b911dbb208455af2fc
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/22103
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Jiajie Hu <jiajie.hu@intel.com>
diff --git a/DEPS b/DEPS
index ba943b7..6808987 100644
--- a/DEPS
+++ b/DEPS
@@ -212,7 +212,7 @@
   {
     'name': 'binutils',
     'pattern': 'src/third_party/binutils',
-    'condition': 'host_os == "linux"',
+    'condition': 'host_os == "linux" and dawn_standalone',
     'action': [
         'python',
         'third_party/binutils/download.py',