If the output file is not specified make the modifications in-place
(like binutils objcopy does). In particular, this fixes
the behavior of Clang -gsplit-dwarf (if Clang is configured to use llvm-objcopy),
previously it was creating .dwo files, but still leaving *dwo* sections in
the original binary.
Test plan: make check-all
Differential revision: https://reviews.llvm.org/D42873
llvm-svn: 324783
Alexander Shaposhnikov