FPC compilers are generally per architecture, not per target, so the x86_64 linux compiler (ppcx64) can also compile for win64.
But you need to build the libraries.
Copy relevant units/ tree from a Windows install and putting it in /usr/lib/fpc/3.3.1/units/x86_64-win64 might be the easiest way to get started.
It should be the same 3.3.1 though, since 3.3.1 is a rolling development version