trusty: Add host build for rpmb_dev

Building rpmb_dev as a host tool in soong makes it easy to package for
acloud, rather than building it in the Trusty build system and uploading
that to the remote instance.

Test: m
Bug: 354771029
Change-Id: I3b7f623238957ae3b25524d424025fd08f805657
1 file changed