Linux: Enable multi-threading with the gold linker.

build/config/compiler/BUILD.gn

Index: build/config/compiler/BUILD.gn
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index 164b97d26260f3e238834c36ffad1e9e53037f5c..9739093b64a7a1cbe4e287783288c24e3db8af00 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -380,10 +380,8 @@ config("compiler") {
       # https://groups.google.com/a/chromium.org/group/chromium-dev/browse_thread/thread/281527606915bb36
       # Only apply this to the target linker, since the host
       # linker might not be gold, but isn't used much anyway.
-      # TODO(raymes): Disable threading because gold is frequently
-      # crashing on the bots: crbug.com/161942.
-      #"-Wl,--threads",
-      #"-Wl,--thread-count=4",
+      "-Wl,--threads",
+      "-Wl,--thread-count=4",
     ]
   }