I'm not using XAMPP, I'm just using MySql57 as a Windows-Service, so directly downloaded and installed from Oracle.
As other guys already mentioned here it's just rebuilding some of the externals, especially the cryptopp(cryptlib) which is only needed if youre using the improved paket encryption. (For Server)
I remember that @Yiv was helping me years ago to get the serversource running on windows, because there some differences in some methods for Windows and BSD.
So some parts of the code needs to be changed via compiler defines in VS (sth. like _WIN32)
Im not sure how it's about other sources like mainline_sg or sth else...