It looks like on some host-triples the result of a valist related expr can be
a LazyCompoundVal. Handle that case in the check.

Patch by Abramo Bagnara!


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@297619 91177308-0d34-0410-b5e6-96231b3b80d8