Revert "[optimizing] Enable x86 long support."

Few libcore failures.

This reverts commit b4ba354cf8d22b261205494875cc014f18587b50.

Change-Id: I4a28d853e730dff9b69aec9555505803cf2fcd63
diff --git a/compiler/optimizing/optimizing_compiler.cc b/compiler/optimizing/optimizing_compiler.cc
index 9971daf..eb98424 100644
--- a/compiler/optimizing/optimizing_compiler.cc
+++ b/compiler/optimizing/optimizing_compiler.cc
@@ -523,7 +523,7 @@
                             dex_file,
                             dex_compilation_unit,
                             &pass_info_printer);
-  } else if (shouldOptimize && can_allocate_registers) {
+  } else if (shouldOptimize && RegisterAllocator::Supports(instruction_set)) {
     LOG(FATAL) << "Could not allocate registers in optimizing compiler";
     UNREACHABLE();
   } else {