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

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 b5231b1537587a51bdcf520f1adb0afc7eb91cda..872641b7fe5bc5da18fcf9053575538146fea3cb 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -833,11 +833,15 @@ config("runtime_library") {
 config("default_warnings") {
   cflags = []
   cflags_cc = []
+  ldflags = []
 
   if (is_win) {
     if (treat_warnings_as_errors) {
       cflags += [ "/WX" ]
     }
+    if (fatal_linker_warnings) {
+      ldflags += [ "/WX" ]
+    }
 
     cflags += [
       # Assume UTF-8 by default to avoid code page dependencies.