This diff adds support for LLVM bitcode objects to llvm-libtool-darwin.
Test plan: make check-all
Differential revision: https://reviews.llvm.org/D88722
Add support for flattening archives while creating static libraries.
Hence, can now pass archives as input in addition to Mach-O binaries.
Furthermore, archives themselves must only conatain Mach-O binaries. As
per cctools' libtool's behavior, llvm-libtool-darwin does not flatten
archives recursively.
Reviewed by alexshap, smeenai, jhenderson
Differential Revision: https://reviews.llvm.org/D83520