I hate it when bugpoint is all ready to give me a bytecode file, then crashes

I hate it when bugpoint is all ready to give me a bytecode file, then crashes
in final cleanups.  Then you had to run the whole mess again with
-disable-final-cleanups.

This makes bugpoint run the cleanups in a protected environment so that if
they crash, bugpoint itself doesn't crash.  This makes things much happier,
implements a FIXME, and gets rid of YABPO (yet another bugpoint option).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@9743 91177308-0d34-0410-b5e6-96231b3b80d8