if we are given a Layout object, even in cases when the value is not fixed.
This will be needed by the final patch for the dwarf .loc support to size a
new MCDwarf fragment needed to build and emit dwarf line number tables.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@115155 91177308-0d34-0410-b5e6-96231b3b80d8