ART: Turn off ARM64 compilation for now

When no compiler filter string is given to dex2oat for ARM64,
default to interpreter.

Change-Id: I2a97e07b1d9b75a04aafe4aaa4437e500bdaf202
diff --git a/dex2oat/dex2oat.cc b/dex2oat/dex2oat.cc
index ad796f8..874c324 100644
--- a/dex2oat/dex2oat.cc
+++ b/dex2oat/dex2oat.cc
@@ -1017,7 +1017,7 @@
   }
 
   if (compiler_filter_string == nullptr) {
-    if (instruction_set == kX86_64 || instruction_set == kMips) {
+    if (instruction_set == kX86_64 || instruction_set == kArm64 || instruction_set == kMips) {
       // TODO: implement/fix compilers for these architectures.
       compiler_filter_string = "interpret-only";
     } else if (image) {