Remove unused private member variables found by clang -Wunused-private-field

test/cctest/test-api.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 17975 matching lines @@
       // Set value and signal semaphore
       test_->sem_value_ = 1;
       test_->sem_->Signal();
     }
 
     static void SignalHandler(int signal) {
     }
 
    private:
      ThreadInterruptTest* test_;
-     struct sigaction sa_;
   };
 
   i::Semaphore* sem_;
   volatile int sem_value_;
 };
 
 
 THREADED_TEST(SemaphoreInterruption) {
   ThreadInterruptTest().RunTest();
 }
 #endif  // WIN32