[llvm-objcopy] Add --keep-symbols option

Differential Revision: https://reviews.llvm.org/D60054

Change-Id: I8ed5491cd553d3dc1909b2c57eebbba3d3ab1c74
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@357418 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed