AArch64: Add arm64 runtime support.

Adds support for arm64 to ART. Assembler stubs are sufficient for
down calls into interpreter. JNI compiler and generics are not finished.

Basic Generic JNI functionality.

Change-Id: I4a07c79d1e037b9f5746673480e32cf456867b82
diff --git a/compiler/driver/compiler_driver.cc b/compiler/driver/compiler_driver.cc
index e601a1b..59754d5 100644
--- a/compiler/driver/compiler_driver.cc
+++ b/compiler/driver/compiler_driver.cc
@@ -1871,7 +1871,7 @@
   if ((access_flags & kAccNative) != 0) {
     // Are we interpreting only and have support for generic JNI down calls?
     if ((compiler_options_->GetCompilerFilter() == CompilerOptions::kInterpretOnly) &&
-        (instruction_set_ == kX86_64)) {
+        (instruction_set_ == kX86_64 || instruction_set_ == kArm64)) {
       // Leaving this empty will trigger the generic JNI version
     } else {
       compiled_method = compiler_->JniCompile(*this, access_flags, method_idx, dex_file);