[llvm-objcopy] Add --strip-all option to llvm-objcopy

This change adds a slightly less extreme form of stripping. It should
remove any section that starts with ".debug" and should remove any
symbol table or relocations. In general this strips out most of the
stuff you don't need to execute but leaves a number of things around.
This behavior has been designed to be compatible with GNU strip/objcopy
--strip-all so that anywhere you currently use --strip-all you should be
able to use llvm-objcopy as a drop in replacement.

Differential Revision: https://reviews.llvm.org/D39769

llvm-svn: 318092