[llvm-objcopy] Add support for removing sections

This change adds support for removing sections using the -R field (as
GNU objcopy does as well). This change should let us add many helpful
tests and is a proper stepping stone for adding more general kinds of
stripping.

Differential Revision: https://reviews.llvm.org/D38260

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@315346 91177308-0d34-0410-b5e6-96231b3b80d8
12 files changed