Prevent building with MSVC 14.24

MSVC 14.24 miscompiles some of LLVM's code, which makes at least these tests fail:

    LLVM :: MC/MachO/gen-dwarf-cpp.s
    LLVM :: MC/MachO/gen-dwarf-macro-cpp.s
    LLVM :: MC/MachO/gen-dwarf-producer.s
    LLVM :: MC/MachO/gen-dwarf.s

It seems better to diagnose that at build time. Since both the previous
and the next version have a fix, this might be good enough and we might
not need a real workaround. (We ran into this at
https://crbug.com/1045948)

If you hit this, use either a newer or an older version of MSVC,
or use clang-cl as host compiler.

Differential Revision: https://reviews.llvm.org/D73550