I found one person in the archive who had had exactly this and there were no responses...
I have renamed my homepage to (say) "Terry".
When I dev/build, then SS helpfully creates a new page called "Home" with the "Welcome to Silverstripe bla bla" message and makes that my homepage. This is very annoying!
Why am I forbidden from renaming my homepage? ... No. Hang about, actually I'm not. I *can* rename it. It's a feature! So why then does dev/build make me a new one?
If I just change the navigation name to Terry, then everything is fine.
It's been suggested elsewhere that there's a 'Homepage' tickbox, and in fact I searched for this in the CMS to begin with.