Merging r338934:

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r338934 | vsapsai | 2018-08-04 01:12:37 +0200 (Sat, 04 Aug 2018) | 29 lines

[Preprocessor] Allow libc++ to detect when aligned allocation is unavailable.

Libc++ needs to know when aligned allocation is supported by clang, but is
otherwise unavailable at link time. Otherwise, libc++ will incorrectly end up
generating calls to `__builtin_operator_new`/`__builtin_operator_delete` with
alignment arguments.

This patch implements the following changes:

* The `__cpp_aligned_new` feature test macro to no longer be defined when
  aligned allocation is otherwise enabled but unavailable.

* The Darwin driver no longer passes `-faligned-alloc-unavailable` when the
  user manually specifies `-faligned-allocation` or `-fno-aligned-allocation`.

* Instead of a warning Clang now generates a hard error when an aligned
  allocation or deallocation function is referenced but unavailable.

Patch by Eric Fiselier.

Reviewers: rsmith, vsapsai, erik.pilkington, ahatanak, dexonsmith

Reviewed By: rsmith

Subscribers: Quuxplusone, cfe-commits

Differential Revision: https://reviews.llvm.org/D45015


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git-svn-id: https://llvm.org/svn/llvm-project/cfe/branches/release_70@339660 91177308-0d34-0410-b5e6-96231b3b80d8