PassManagerBuilder: Remove effectively dead 'StripDebug' option

`StripDebug` was only used by tools/opt/opt.cpp in
`AddStandardLinkPasses()`, but opt.cpp adds the same pass based on its
command-line flag before it calls `AddStandardLinkPasses()`.  Stripping
debug info twice isn't very useful.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232765 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed