Enables first codegen test on arm64.

runtime/vm/unit_test.cc

Index: runtime/vm/unit_test.cc
===================================================================
--- runtime/vm/unit_test.cc	(revision 35315)
+++ runtime/vm/unit_test.cc	(working copy)
@@ -169,9 +169,6 @@
 }
 
 
-// TODO(zra): Remove once supported.
-#if !defined(TARGET_ARCH_ARM64)
-
 CodeGenTest::CodeGenTest(const char* name)
   : function_(Function::ZoneHandle()),
     node_sequence_(new SequenceNode(Scanner::kNoSourcePos,
@@ -209,6 +206,9 @@
 }
 
 
+// TODO(zra): Remove once supported.
+#if !defined(TARGET_ARCH_ARM64)
+
 LocalVariable* CodeGenTest::CreateTempConstVariable(const char* name_part) {
   char name[64];
   OS::SNPrint(name, 64, ":%s", name_part);