win: Avoid 'warning C4068: unknown pragma'

client/crashpad_info.h

 // Copyright 2014 The Crashpad Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 30 matching lines @@
     simple_annotations_ = simple_annotations;
   }
 
   static const uint32_t kSignature = 'CPad';
 
  private:
   // The compiler won’t necessarily see anyone using these fields, but it
   // shouldn’t warn about that. These fields aren’t intended for use by the
   // process they’re found in, they’re supposed to be read by the crash
   // reporting process.
+#if defined(__clang__)
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wunused-private-field"
+#endif
+
   // Fields present in version 1:
   uint32_t signature_;  // kSignature
   uint32_t size_;  // The size of the entire CrashpadInfo structure.
   uint32_t version_;  // kVersion
   uint32_t padding_0_;
   SimpleStringDictionary* simple_annotations_;  // weak
+
+#if defined(__clang__)
 #pragma clang diagnostic pop
+#endif
 
   DISALLOW_COPY_AND_ASSIGN(CrashpadInfo);
 };
 
 }  // namespace crashpad
 
 #endif  // CRASHPAD_CLIENT_CRASHPAD_INFO_H_