Revert "Revert "ART: Mterp for arm64""

Looks like some of our assemblers disagree on valid arm64 assembly syntax
Force use of clang for art runtime.  In a subsequent CL, will use form
that both gcc and clang accept.

This reverts commit 43f3fb960bce978df699c8a68a972be2a0d0d221.

Change-Id: Ice83072171ab502c43d492e2238b446c4814ea67
diff --git a/runtime/interpreter/mterp/arm64/op_const.S b/runtime/interpreter/mterp/arm64/op_const.S
new file mode 100644
index 0000000..031ede1
--- /dev/null
+++ b/runtime/interpreter/mterp/arm64/op_const.S
@@ -0,0 +1,9 @@
+    /* const vAA, #+BBBBbbbb */
+    lsr     w3, wINST, #8               // w3<- AA
+    FETCH w0, 1                         // w0<- bbbb (low
+    FETCH w1, 2                         // w1<- BBBB (high
+    FETCH_ADVANCE_INST 3                // advance rPC, load wINST
+    orr     w0, w0, w1, lsl #16         // w0<- BBBBbbbb
+    GET_INST_OPCODE ip                  // extract opcode from wINST
+    SET_VREG w0, w3                     // vAA<- w0
+    GOTO_OPCODE ip                      // jump to next instruction