llvm-dwarfdump: reorder dwo sections to immediately proceed their non-dwo equivalents

This makes it easier to write a test that's mostly shared between
fission and non-fission (using FileCheck's multiple prefix support).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198806 91177308-0d34-0410-b5e6-96231b3b80d8