Testing no /DUNICODE assumptions with Win more configs bots.

This CL will avoid regressions after the cleanup done in
https://webrtc-review.googlesource.com/c/src/+/128904.

Bug: None
Change-Id: Id01f554a6fb0972139e7810b7523c91321398c0f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/130100
Reviewed-by: Oleh Prypin <oprypin@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27328}
diff --git a/BUILD.gn b/BUILD.gn
index f1ac0bb..f299446 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -361,6 +361,13 @@
     # Used in Chromium's overrides to disable logging
     defines += [ "WEBRTC_UNSAFE_FUZZER_MODE" ]
   }
+
+  if (!build_with_chromium && rtc_win_undef_unicode) {
+    cflags += [
+      "/UUNICODE",
+      "/U_UNICODE",
+    ]
+  }
 }
 
 config("common_objc") {