[lld-macho] Implement -dependency_info (partially - more opcodes needed)

Bug: https://bugs.llvm.org/show_bug.cgi?id=49278
The flag is not well documented, so this implementation is based on observed behaviour.

When specified, `-dependency_info <path>` produced a text file containing information pertaining to the current linkage, such as input files, output file, linker version, etc.

This file's layout is also not documented, but it seems to be a series of null ('\0') terminated strings in the form `<op code><path>`

`<op code>` could be:
   `0x00` : linker version
   `0x10` : input
   `0x11` : files not found(??)
   `0x40` : output

`<path>` : is the file path, except for the linker-version case.

(??) This part is a bit unclear. I think it means all the files the linker attempted to look at, but could not find.

Differential Revision: https://reviews.llvm.org/D98559