Added Address Sanitizer clang config for x86_64.

Without this, binaries built for an x64 target with Address Sanitizer enabled
fail to execute at runtime, failing with the error message "No such file or
directory".

Test: 1) Build any Android target that has asan enabled, such as statsd, on
any lunch target with suffix "_x86_64-eng". 2) Run 'file' on the generated
executable. 3) You should see "interpreter /system/bin/linker_asan64" rather
than "interpreter --gc-sections"

Bug: 111667639

Change-Id: I5d7e7f307d954d4cd48ff88a7d9d6a5732276296