By using `_LIBCPP_PREFERRED_OVERLOAD` we make
sure that a given overload is a better match
than an otherwise equally good function
declaration.

Why is there an equally good function
declaration in the first place? Underlying the
Windows SDK is the UCRT, the universal C runtime,
which clang-cl makes use of. The UCRT should
provide only C library headers, but does on top
comes with overloads for all cv-unqualified floating
point types (float, double, long double) for
`std::signbit()` in https://github.com/microsoft/win32metadata/blob/e012b29924c53aa941fc010850b68331b0c3ea80/generation/WinSDK/RecompiledIdlHeaders/ucrt/corecrt_math.h#L309-L322.
In a certain way, this can be seen as a deviation
from the C standard. We need to work around it.