bugpoint: Return Errors instead of passing around strings
This replaces the threading of `std::string &Error` through all of
these APIs with checked Error returns instead. There are very few
places here that actually emit any errors right now, but threading the
APIs through will allow us to replace a bunch of exit(1)'s that are
scattered through this code with proper error handling.
This is more or less NFC, but does move around where a couple of error
messages are printed out.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@280720 91177308-0d34-0410-b5e6-96231b3b80d8
10 files changed