To cross-compile, you have to build a cross-compiler.
The FPC wiki contains a lot of info on how to accomplish that.
An easy start will also be possible with fpcupdeluxe.
First, use fpcupdeluxe to install a FPC and Lazarus version of your choice in a location (directory) of your choice). You might try FPC and Lazarus trunk. But latest fixes of both is also a good choice.
Second, use fpcupdeluxe to build a cross-compiler.
When the two step above have been successfully finished (keep thumbs crossed), you can have a look at the various settings on how this has been setup (e.g. fpc.cfg).