Use RTC_UNUSED instead of conditional compilation in BWE simulator tool.

webrtc/typedefs.h

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 62 matching lines @@
 #if defined(__GNUC__) || defined(__clang__)
 #define WARN_UNUSED_RESULT __attribute__ ((__warn_unused_result__))
 #else
 #define WARN_UNUSED_RESULT
 #endif
 #endif  // WARN_UNUSED_RESULT
 
 // Put after a variable that might not be used, to prevent compiler warnings:
 //   int result ATTRIBUTE_UNUSED = DoSomething();
 //   assert(result == 17);
+// Deprecated since it only works with GCC & clang. See RTC_UNUSED below.
+// TODO(terelius): Remove.
 #ifndef ATTRIBUTE_UNUSED
 #if defined(__GNUC__) || defined(__clang__)
 #define ATTRIBUTE_UNUSED __attribute__ ((__unused__))
 #else
 #define ATTRIBUTE_UNUSED
 #endif
 #endif
 
 // Macro to be used for switch-case fallthrough (required for enabling
 // -Wimplicit-fallthrough warning on Clang).
 #ifndef FALLTHROUGH
 #if defined(__clang__)
 #define FALLTHROUGH() [[clang::fallthrough]]
 #else
 #define FALLTHROUGH() do { } while (0)
 #endif
 #endif
 
 #ifndef NO_RETURN
 // Annotate a function that will not return control flow to the caller.
 #if defined(_MSC_VER)
 #define NO_RETURN __declspec(noreturn)
 #elif defined(__GNUC__)
 #define NO_RETURN __attribute__ ((__noreturn__))
 #else
 #define NO_RETURN
 #endif
 #endif
 
+// Prevent the compiler from warning about an unused variable. For example:
+//   int result = DoSomething();
+//   assert(result == 17);
+//   RTC_UNUSED(result);
+// Note: In most cases it is better to remove the unused variable rather than
+// suppressing the compiler warning.
+#ifndef RTC_UNUSED
+#define RTC_UNUSED(x) static_cast<void>(x)
+#endif  // RTC_UNUSED
+
 #endif  // WEBRTC_TYPEDEFS_H_