Disable sanitizers for the yasm build tool.

This is only used during building, there's not a good reason to have
the sanitizers enabled since it will significantly slow down the
actual build process and seems to try to allocation nearly a terabyte
of memory at some points.

BUG=861418
TEST=none

Change-Id: I8d2116fbcee6dff2f1ecc422fbca5ef506fad6dd
Reviewed-on: https://chromium-review.googlesource.com/c/1257671
Reviewed-by: Evgeniy Stepanov <eugenis@chromium.org>
Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#596035}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: f67c656ca329a21f8fd3c63a536c16770097b3a2
diff --git a/BUILD.gn b/BUILD.gn
index b261e4d..35a85b1 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -41,7 +41,11 @@
 
     # Don't define _DEBUG. Modest savings, but good for consistency.
     "//build/config:debug",
+
+    # Don't enable sanitizers for build tools. They slow down the overall build.
+    "//build/config/sanitizers:default_sanitizer_flags",
   ]
+
   configs_to_add += [
     "//build/config:release",
     "//build/config/compiler:optimize_max",