acloud: Add in acloud linux-x86 prebuilt.

Built from
https://android.googlesource.com/platform/tools/acloud/+/c64f3438b5a8aec7ca133970a1fcd79c768ae909

We'll also want acloud as part of the build artifacts, so add it to
droidcore.

Bug: None
Test: m droidcore
Change-Id: Iceaf0cba865c0b6bd8b9a84c76e87fce8f57b14d