Create msvs_large_pdb workaround.

test/win/large-pdb/dllmain.cc

Index: test/win/large-pdb/dllmain.cc
diff --git a/test/win/shard/hello4.cc b/test/win/large-pdb/dllmain.cc
similarity index 59%
copy from test/win/shard/hello4.cc
copy to test/win/large-pdb/dllmain.cc
index a94df194999a38e80cde7e2a7205a9f6a39601cd..14875623e833b6fd6667e800e5c722214999c9dc 100644
--- a/test/win/shard/hello4.cc
+++ b/test/win/large-pdb/dllmain.cc
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-int f4() {
-  return 0;
+#include <windows.h>
+
+BOOL WINAPI DllMain(HINSTANCE hinstance, DWORD reason, LPVOID reserved) {
+  return TRUE;
 }