Fuchsia: Fix arm64 build

runtime/vm/assembler_arm64.cc

 // Copyright (c) 2014, 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.
 
 #include "vm/globals.h"  // NOLINT
 #if defined(TARGET_ARCH_ARM64)
 
 #include "vm/assembler.h"
 #include "vm/cpu.h"
 #include "vm/longjump.h"
 #include "vm/runtime_entry.h"
 #include "vm/simulator.h"
 #include "vm/stack_frame.h"
 #include "vm/stub_code.h"
 
-// An extra check since we are assuming the existence of /proc/cpuinfo below.
-#if !defined(USING_SIMULATOR) && !defined(__linux__) && !defined(ANDROID) && \
-    !TARGET_OS_IOS
-#error ARM64 cross-compile only supported on Linux
-#endif
-
 namespace dart {
 
 DECLARE_FLAG(bool, check_code_pointer);
 DECLARE_FLAG(bool, inline_alloc);
 
 DEFINE_FLAG(bool, use_far_branches, false, "Always use far branches");
 
 
 Assembler::Assembler(bool use_far_branches)
     : buffer_(),
@@ skipping 1396 matching lines @@
     add(base, array, Operand(index, LSL, shift));
   }
   const OperandSize size = Address::OperandSizeFor(cid);
   ASSERT(Address::CanHoldOffset(offset, Address::Offset, size));
   return Address(base, offset, Address::Offset, size);
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64