Don't pass llvm::errs() all over the place. Diagnostics always go to stderr.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@185657 91177308-0d34-0410-b5e6-96231b3b80d8
Add 'not' to command lines that are expected to fail.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@185658 91177308-0d34-0410-b5e6-96231b3b80d8