[llvm-objcopy] Dwarf .debug section compression support (zlib, zlib-gnu).
Second Attempt. Alignment issues resolved. zlib::isAvailable() detected.
Usage:
llvm-objcopy --compress-debug-sections=zlib foo.o
llvm-objcopy --compress-debug-sections=zlib-gnu foo.o
In both cases the debug section contents is compressed with zlib. In the GNU
style case the header is the "ZLIB" magic string followed by the uint64 big-
endian decompressed size. In the non-GNU mode the header is the
Elf(32|64)_Chdr.
Decompression support is coming soon.
Differential Revision: https://reviews.llvm.org/D49678
llvm-svn: 341607