Use the /WX flag to have link warnings treated as errors.

build/config/win/BUILD.gn

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/clang/clang.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/win/visual_studio_version.gni")
 import("//build/toolchain/toolchain.gni")
 
@@ skipping 220 matching lines @@
       "$visual_studio_path\VC\atlmfc\lib",
     ]
   }
 }
 
 # This default linker setup is provided separately from the SDK setup so
 # targets who want different library configurations can remove this and specify
 # their own.
 config("common_linker_setup") {
   ldflags = [
+    "/fastfail",
     "/FIXED:NO",
     "/ignore:4199",
     "/ignore:4221",
     "/NXCOMPAT",
   ]
 
-  ldflags += [
-    # Tell the linker to crash on failures.
-    "/fastfail",
-  ]
-
   # ASLR makes debugging with windbg difficult because Chrome.exe and
   # Chrome.dll share the same base name. As result, windbg will name the
   # Chrome.dll module like chrome_<base address>, where <base address>
   # typically changes with each launch. This in turn means that breakpoints in
   # Chrome.dll don't stick from one launch to the next. For this reason, we
   # turn ASLR off in debug builds.
   if (is_debug) {
     ldflags += [ "/DYNAMICBASE:NO" ]
   } else {
     ldflags += [ "/DYNAMICBASE" ]
@@ skipping 161 matching lines @@
 
 # Internal stuff --------------------------------------------------------------
 
 # Config used by the MIDL template to disable warnings.
 config("midl_warnings") {
   if (is_clang) {
     # MIDL generates code like "#endif !_MIDL_USE_GUIDDEF_".
     cflags = [ "-Wno-extra-tokens" ]
   }
 }