[Remarks][Driver] Use the specified format in the remarks file extension

By default, use `.opt.yaml`, but when a format is specified with
`-fsave-optimization-record=<format>`, use `.opt.<format>`.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@363627 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed