Summary: I had added support for compressing dwarf sections in a prior commit,
this one adds support for decompressing. Usage is:
llvm-objcopy --decompress-debug-sections input.o output.o
Reviewers: jakehehrlich, jhenderson, alexshap
Reviewed By: jhenderson
Differential Revision: https://reviews.llvm.org/D51841
llvm-svn: 343451