[lldb] fix build issue on MSVC because of missing byte-swap builtins

The `__builtin_bswap{32,64}()` builtins (introduced in commit e07a421d)
are missing from MSVC, which causes build errors when compiling LLDB on
Windows (tested with MSVC 19.34.31943.0).  This patch replaces the
builtins with either MSVC's `_byteswap_u{long,64}()` or the original
builtins, or the `bswap_{32,64}()` functions from byteswap.h, depending
on which ones are available.

Reviewed By: bulbazord

Differential Revision: https://reviews.llvm.org/D148541