Implement resolve-system-dependencies in C++

[pikajude]

Instead of serializing a hashmap to a file as Perl does (which would require an external library dependency), this script stores the dependency list for each lib separately in a cache directory. This should be faster than the old implementation because no resolving is done after the first time the script runs.

Accepting code review as my C++ is not very clean.

[knedlsepp]

Instead of using a const reference parameter and doing explicit copying, you could directly accept the lib argument via value.

[copumpkin]

At the highest level, I'd suggest using mmap because it saves you from doing 90% of the nasty seeking/reading/sizeof-ing. You map the object into memory and then the various structs already point at the correct data. That's how dyld does it, and I think it'll make your life a lot simpler.

[copumpkin]

(not that I'd block merging this because you didn't use mmap, but I think it'd be a bit more pleasant)

[edolstra]

This lacks error checking. I would use C++ <iostream>, or read the whole file into memory using readFile() for simplicity.

[domenkozar]

@pikajude does this address #941?

[domenkozar]

Also relevant is #786

[pikajude]

@domenkozar #941 will no longer apply because otool is not used or even required in this rewrite (the mach-o files are directly read by the script instead). #786 looks to be a fundamental problem with pre-build hooks in general, and as such will require more investigation.

@edolstra @copumpkin I have rewritten the script to use mmap, meaning there should be a little less fiddling around with FILE*s.