Moritz Angermann authored Mar 21, 2017 and Ben Gamari committed Mar 26, 2017

This adds ocInit_MachO function, used to populate the extended
ObjectCode structure, and the corresponding stgFree.

It also adds defines for iOS, such that MachO.o is also compiled for iOS
targets.

Depends on D3239

---

This is just one of the pieces for the rts linker
support for ios (aarch64-macho)

---

The following diagram and legend tries to explain the dependencies a
bit:
```
  .- D3240
  v
D3255 <- D3252 <- This <- D3239
  ^
  '- D3238
```

- In D3238 we started allowing preloading object code with mmap
  in iOS, where we can't have r+w+x.
- In D3239 we introduced a richer extension of the object code
  data type to make working with mach-o files easier.
- In D3240 we set the stage to allow loading archives (.a) on iOS
- In D3251 we added init and deinit functions to populate and
  depopulate the enriched object code data structure for mach-o
  files.
- In D3252 we refactored most of the MachO.c file to use the
  new types and data structure.
- in D3255 we finally introduce the aarch64-mach-o linker.

Reviewers: rwbarton, bgamari, austin, erikd, simonmar

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D3251