mac: Only call system aligned_alloc() with the 11.0+ SDK.
mac: Only call system aligned_alloc() with the 11.0+ SDK.

The 10.15 SDK only declares it for C++17 and C11.  In Chromium, we only
call this from .cc files, and these are C++14 still for now.

The 11.0 SDK declares it independent of language version (as long as
__DARWIN_C_LEVEL >= __DARWIN_C_FULL, which it is by default, at least
on macOS).

So this calls the system version in fewer scenarios than possible,
but it keeps the preprocessor checks fairly small.

Bug: chromium:1098741
Change-Id: I1e30f88bb040876bca2b59adee0a1cff33b9ff03

GPUOpen-LibrariesAndSDKs/VulkanMemoryAllocator,GPUOpen-LibrariesAndSDKs/VulkanMemoryAllocator,GPUOpen-LibrariesAndSDKs/VulkanMemoryAllocator