[libFuzzer][Windows]Use build config to stop instrumenting LF with ASAN

Since we can't rely on no_sanitize attributes on Windows, use the gn
configs to ensure LF isn't instrumented with ASAN.
This fix is hopefully temporary, ideally we can get clang-cl to respect
the no_sanitize attribute.

Bug: 883948
Change-Id: Ia4854d5f5b9148d175fa2f5f90bd9b34f064e064
Reviewed-on: https://chromium-review.googlesource.com/1249150Reviewed-by: Max Moroz <mmoroz@chromium.org>
Commit-Queue: Jonathan Metzman <metzman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594840}

third_party/libFuzzer/BUILD.gn

@@ -41,7 +41,11 @@ source_set("libfuzzer") {
   ]
 
   configs -= fuzzing_engine_remove_configs
-  configs += fuzzing_engine_add_configs
+  if (!is_win) {
+    # TODO(crbug.com/883948): Remove the check for is_win when libFuzzer on
+    # Windows handles the nosanitize attribute properly.
+    configs += fuzzing_engine_add_configs
+  }
 }
 
 source_set("afl_driver") {