Fix MinGW cross compilation
Fix MinGW cross compilation

Some file systems are case sensitive.

    In file included from maxminddb_test_helper.c:11:
    maxminddb_test_helper.h:16:10: fatal error: Winsock2.h: No such file or directory
    16 | #include <Winsock2.h>
        |          ^~~~~~~~~~~~
maxmind/libmaxminddb,maxmind/libmaxminddb,maxmind/libmaxminddb