[lldb] Re-add compile-time checks for SPI in HosInfoMacOSX

There were some checks removed previously in
bc196970.

However, all these SPIs are actually defined in macOS 12 and onward, not
macOSX 10.12 as the previous commit would suggest. As a result, if you
have access to these SPIs lldb will fail to compile correctly.

Instead of adding back the __builtin_availability checks, it seems
easier just to check the minimum deployment target with Availability
macros.

Differential Revision: https://reviews.llvm.org/D156838