cmake: [win32] Update cmake files

cmake: [win32] Update cmake files

We'll update the cmake files in order to be able to build ceph
components for Windows targets.

Cross compiling using MINGW is the easiest approach for now.
Subsequently, we'll add support for Clang and MSVC.

This patch provides the following changes:
* include winsock2.h, which provides ntohl on Windows
* avoid unsupported compiler flags when using msvc
* add a custom toolchain file for mingw
* update install command for ceph-common in order to work with mingw
* avoid running test sample when cross compiling
* link against the ws_32 lib
* set argeted Windows version
* skip yasm checks when targeting Windows
* allow multiple redefinitions when using mingw, picking the first one.
  this is a workaround for a mingw TLS bug:
  https://sourceforge.net/p/mingw-w64/bugs/816/

Signed-off-by: Alin Gabriel Serdean <aserdean@cloudbasesolutions.com>
Signed-off-by: Lucian Petrut <lpetrut@cloudbasesolutions.com>