Get `gn gen` to succeed on Windows

third_party/sqlite/sqlite3.h

Index: third_party/sqlite/sqlite3.h
diff --git a/third_party/sqlite/sqlite3.h b/third_party/sqlite/sqlite3.h
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index 0000000000000000000000000000000000000000..27094db29182c74c90af1675e700fc22360e905a
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+++ b/third_party/sqlite/sqlite3.h
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+// Copyright (c) 2010 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.
+
+#ifndef THIRD_PARTY_SQLITE_SQLITE3_H_
+#define THIRD_PARTY_SQLITE_SQLITE3_H_
+#pragma once
+
+// This is a shim header to include the right sqlite3 header.
+// Use this instead of referencing the sqlite3 header directly.
+
+#if defined(USE_SYSTEM_SQLITE)
+#include <sqlite3.h>
+#else
+#include "third_party/sqlite/amalgamation/sqlite3.h"
+#endif
+
+#endif  // THIRD_PARTY_SQLITE_SQLITE3_H_