init: check the arguments of builtins during the build

Host init verifier already checks that the names and number of
arguments for builtins are correct, but it can check more.  This
change ensures that property expansions are well formed, and that
arguments that can be parsed on the host are correct.  For example it
checks that UIDs and GIDs exist, that numerical values can be parsed,
and that rlimit strings are correct.

Test: build

Change-Id: Ied8882498a88a9f8324db6b8d1020aeeccc8177b