Use dex2oat64 on 64-bit-only builds

dexopt defaults to dex2oat32 unless instructed otherwise. Since
dex2oat32 doesn't exist on a 64-bit-only build, make sure dex2oat64
is selected instead.

Test: boot aosp_cf_x86_64_only_phone and check that installd doesn't
  try to use dex2oat32
Change-Id: Ia67e746894684a52a4e5b765bfde0f6dd0efbf6e
diff --git a/target/product/core_64_bit_only.mk b/target/product/core_64_bit_only.mk
index 53c9c74..061728f 100644
--- a/target/product/core_64_bit_only.mk
+++ b/target/product/core_64_bit_only.mk
@@ -25,6 +25,9 @@
 # Set the zygote property to select the 64-bit script.
 # This line must be parsed before the one in core_minimal.mk
 PRODUCT_VENDOR_PROPERTIES += ro.zygote=zygote64
+# A 64-bit-only platform does not have dex2oat32, so make sure dex2oat64 is
+# used for dexopt.
+PRODUCT_VENDOR_PROPERTIES += dalvik.vm.dex2oat64.enabled=true
 
 TARGET_SUPPORTS_32_BIT_APPS := false
 TARGET_SUPPORTS_64_BIT_APPS := true