cros_setup_toolchains: Switch aarch64 linker to gold.

Use gold as the default linker for aarch64

BUG=chromium:779127
TEST=kevin/kevin64 builders passed.

CQ-DEPEND=CL:1338359

Change-Id: Ib2d12d53288a39ac03fb85baf906589fe5650c49
Reviewed-on: https://chromium-review.googlesource.com/1337436
Commit-Ready: Manoj Gupta <manojgupta@chromium.org>
Tested-by: Manoj Gupta <manojgupta@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/scripts/cros_setup_toolchains.py b/scripts/cros_setup_toolchains.py
index 80baa24..a3fe06a 100644
--- a/scripts/cros_setup_toolchains.py
+++ b/scripts/cros_setup_toolchains.py
@@ -113,6 +113,7 @@
 # Overrides for {gcc,binutils}-config, pick a package with particular suffix.
 CONFIG_TARGET_SUFFIXES = {
     'binutils' : {
+        'aarch64-cros-linux-gnu' : '-gold',
         'armv6j-cros-linux-gnueabi': '-gold',
         'armv7a-cros-linux-gnueabi': '-gold',
         'armv7a-cros-linux-gnueabihf': '-gold',