If we're splitting the dwarf for fission and don't want to use the
integrated assembler then go ahead and still split the dwarf anyhow.

Add two tests, one to exercise existing behavior of not splitting
when we're just emitting assembly files and the other to test
that we split when we're not in integrated as mode.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@183355 91177308-0d34-0410-b5e6-96231b3b80d8