Fix MinGW build issue on example

[zEuS0390]

Fix build issue #2638 on example by adding ws2_32 in these two target_include_directories if the type of compiler is from MinGW.

target_link_libraries(spdlog PUBLIC Threads::Threads $<$<BOOL:${MINGW}>: ws2_32>)
target_link_libraries(spdlog_header_only INTERFACE Threads::Threads $<$<BOOL:${MINGW}>: ws2_32>)

I also made some little changes to "udp_client-windows.h" which uses pragma comment macros only when the Visual C++ compiler is used.

#if defined(_MSC_VER)
#	pragma comment(lib, "Ws2_32.lib")
#	pragma comment(lib, "Mswsock.lib")
#	pragma comment(lib, "AdvApi32.lib")
#endif

[gabime]

Thanks. Please move the cmake change to the example/CMakeLists.txt. The main cmake doesn't deal with the udp sink.

[zEuS0390]

Ok, got it.

[gabime]

Thanks @zEuS0390