ART: Make LOCAL_CLANG architecture dependent for the target

Be selective for which target we compile with Clang. Currently we
only want to compile with Clang for ARM64, which means we need to
be careful about ARM, which is the second architecture for that.

Bug: 15014252

(cherry picked from commit 9689e3768621130b2536564f4e00fcb6b3d25df4)

Change-Id: I312e1caea08f2f3a20304b27f979d3c7b72b0a04
7 files changed