MozillaBuild 1.2's installation dialog's title says "Mozilla Build Setup Setup", and the first message says "Please review the license agreement before installing Mozilla Build Setup". This shows that in the installer source file, the product to install is most likely specified as "Mozilla Build Setup". It should be "Mozilla Build". Also, when the installer detects that the installation directory C:\mozilla-build already exists, it warns that "This will delete everything in C:\mozilla-build. Do you want to continue?" I think "overwrite everything" is more accurate than "delete everything" because the installer doesn't delete the C:\mozilla-build directory before installing.
I've noticed these things too. Thanks for filing this, we'll get it addressed for MozillaBuild 1.3.
Created attachment 323922 [details] [diff] [review] nix the extra setup Trivial patch.