Fix simarm build for newer gcc's

runtime/platform/globals.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef RUNTIME_PLATFORM_GLOBALS_H_
 #define RUNTIME_PLATFORM_GLOBALS_H_
 
 // __STDC_FORMAT_MACROS has to be defined before including <inttypes.h> to
 // enable platform independent printf format specifiers.
 #ifndef __STDC_FORMAT_MACROS
@@ skipping 262 matching lines @@
 
 // DART_NOINLINE tells compiler to never inline a particular function.
 #ifdef _MSC_VER
 #define DART_NOINLINE __declspec(noinline)
 #elif __GNUC__
 #define DART_NOINLINE __attribute__((noinline))
 #else
 #error Automatic compiler detection failed.
 #endif
 
-// DART_UNUSED inidicates to the compiler that a variable/typedef is expected
+// DART_UNUSED indicates to the compiler that a variable or typedef is expected
 // to be unused and disables the related warning.
 #ifdef __GNUC__
 #define DART_UNUSED __attribute__((unused))
 #else
 #define DART_UNUSED
 #endif
 
+// DART_USED indicates to the compiler that a global variable or typedef is used
+// disables e.g. the gcc warning "unused-variable"
+#ifdef __GNUC__
+#define DART_USED __attribute__((used))
+#else
+#define DART_USED
+#endif
+
 // DART_NORETURN indicates to the compiler that a function does not return.
 // It should be used on functions that unconditionally call functions like
 // exit(), which end the program. We use it to avoid compiler warnings in
 // callers of DART_NORETURN functions.
 #ifdef _MSC_VER
 #define DART_NORETURN __declspec(noreturn)
 #elif __GNUC__
 #define DART_NORETURN __attribute__((noreturn))
 #else
 #error Automatic compiler detection failed.
@@ skipping 403 matching lines @@
 // tag in the ICData and check it when recreating the flow graph in
 // optimizing compiler. Enable it for other modes (product, release) if needed
 // for debugging.
 #if defined(DEBUG)
 #define TAG_IC_DATA
 #endif
 
 }  // namespace dart
 
 #endif  // RUNTIME_PLATFORM_GLOBALS_H_