Don't declare all text sections at the start of the .s

Don't declare all text sections at the start of the .s

The code this patch removes was there to make sure the text sections went
before the dwarf sections. That is necessary because MachO uses offsets
relative to the start of the file, so adding a section can change relaxations.

The dwarf sections were being printed at the start just to produce symbols
pointing at the start of those sections.

The underlying issue was fixed in r231898. The dwarf sections are now printed
when they are about to be used, which is after we printed the text sections.

To make sure we don't regress, the patch makes the MachO streamer assert
if CodeGen puts anything unexpected after the DWARF sections.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232842 91177308-0d34-0410-b5e6-96231b3b80d8