When using llvm-libtool-darwin as a drop in replacement for cctools
libtool, Xcode expects you to create a dependency info file. This file
is a very simple format describing the input files, the output files,
and the version of the tool. This logic is mirrored from that of
ld64.lld, which supports creating this file as well. Ideally we could
extract it, but I don't think we want to throw this into one of the
grab-bag libraries given how small the logic is.
Differential Revision: https://reviews.llvm.org/D134322
