I have latest Lazarus/Fpc on my Windows 10 main computer, but also on a number of RaspberryPi (3 and 4) devices. If I create an application on Windows and want to build the same for RPi, then I have to transfer the sources (via Subversion) to the RPi and build there.

And doing so requires me to use VNC to connect to the RPi, which is less than optimal.

Now I wonder how to set up FPC on Windows to cross-compile for Raspberry Pi (arm6/arm7 processor and Debian based Linux)?

The freepascal Wiki articles I have found are either outdated or do not describe enough in detail how one can do this...

So is there some up-to-date article describing it?

I have found this: https://wiki.freepascal.org/Cross_compiling

and it actually mentions RaspberryPi in passing, so I guess that is encouraging.

Since I have RPi units with Lazarus/FPC installed there is also a directory:

$HOME/lib/fpc/3.2.2/units which contains subdir arm-linux

If I tar this arm-linux dir I get a file arm-linux.tgz which is about 52 MB in size.

Do I extract this into my Windows FPC 3.2.2 installation somewhere in order to be able to cross-compile?

Below the Lazarus installation dir /dev/lazarus/2.2.4 I also have this dir:

/dev/lazarus/2.2.4/units/arm-linux and this is 233 KB in size. Do I tar and copy this too into my Windows Lazarus/FPC installation?

It contains only 2 subdirs:
/dev/lazarus/2.2.4/units/arm-linux/gtk2
/dev/lazarus/2.2.4/units/arm-linux/nogui

If so, where do I deposit these files on Windows?
I have used the SourceForge installer to get the Lazarus 2.2.4 installed.

Do I drop them off into a new ...\fpc\3.2.2\units\arm-linux directory even though they came from two different places on the live system?

Grateful for some advice, I have never done this ever before...

If you're not opposed to copying files anyhow, why not setup a script to do the compile for you on the pi?

You just need to setup your pi with ssh keys, then use scp to move the files, ssh to do the login, then just run the shell script to do the compiling.

If you configure the ssh keys properly, you can use windows batch files (or power shell scripts), that would simply copy the files to the right place on the pi, then ssh in (or in your case, vnc I suppose), then just run the script to do the compile.  I don't know if vnc can handle that by itself, so you could use a single script, having never used it, but I do this kind of thing all the time.  I have the pi setup to accept ssh logins so passwords aren't necessary, then I can just scp a file to the pi, then ssh in and uncompress the file, and run the compile command, and it's all done.  Admittedly, it's a two step process, but it works well enough.

I do use FPC, though I don't use lazarus, mostly because it's not really all that compatible with screen readers, so most of my compiling is done via command line, (even on windows development environments), so I don't know if this suggestion can work for you, but I use it regularly when cross compiling for linux/raspberry pi/OSX, and it works well for me.