When given a directory input `llvm-readtapi` traverses through the
directory to find dylibs or tbd files to operate on. TBD files will be
created with the same base file name as the dylib. Symlinks should be
created if the input is one.
This also introduces options to delete input files which are defined as
library files that existed before `readtapi -stubify` was invoked. Also
the ability to delete private libraries where private libraries are in a
predefined file system locations on darwin based platforms.
Stubify broadly takes either tbd files or binary dylibs and turns them
into tbd files. In future patches, stubify will also allow additional
information to be embedded into the final TBD output too.
Add Util APIs to TextAPI for common operations used by readtapi for now.
Merge allows a user to merge different files (tbds for now or dylibs in
the future) to emit out a single tbd with all input contents. This does
require that all inputs represent the same library.
