Thank you all for the feedback. Really appreciated.
Just Like MarkMLI, I am not a Windows user (anymore and for a long time) so I approached this from a Linux point of view.
So, let's start from the beginning
I am on pure Windows so no cygwin, msys, wsl or whatever.
I obtained the gnu tools for windows 64-bit and build and installed the FPC compiler (that went smooth).
Just like on Linux I use a prefab script to launch the compiler. I do this to stop FPC from loading any default config and instead force my own and setup custom environment variables to allow for on the fly switching between compiler versions.
Then I started building Lazarus.
First hurdle is that for some obscure reason the .exe file extension is forced by the makefile. Perhaps something to be expected for a platform that heavily relies on that extension (no it actually isn't, that is why the mime types exist) but it is annoying as hell. So, I had to waste quite some time to work around that issue.
During the IDE build some minor issues popped up, mainly to my own stupidity/setup and I worked around those.
To make sure I got my head screwed on right I did display the make help to make sure what I can and can't use and for sure the make install option is advertised (though it does also tell at the bottom that you /can/ use install for which we can assume it is not required but also not forbidden or unsupported).
The help also tells about changing the install_prefix option to install to another location (and no it does not because the makefile does something completely different than advertised and forces the C:\Lazarus directory upon us. That said, that particular option can be overridden). The makefile lacks creating any of these directories though (and thus fails) :shrugs:
But the real fun starts when using make install and/or make zipinstall, starting with copying the macos app package (or whatever it stands for) but it wasn't build to begin with. At least on Linux that stuff gets build.
So, the makefile bails out on us again.
So, in an attempt to bring marcov up to par: no Lazarus makefiles do not have a sane install command but it could have just like the Linux version does (which has the same requirements).
After more than 10 years of windows absence the only thing I wanted to verify is if there was some progress on that matter but unfortunately it seems that there was some kind of freeze.
So, please don't try to beat around the bush with a copy over the compiled directory, use fpcup or, whatever because I already knew that before I started and it is besides the point (and actually you can't if you want to create a proper installation).
Now, I personally do not mind if something isn't supported but can we please stop advertising that it is ?
2 cents