https://bugs.winehq.org/show_bug.cgi?id=45391
--- Comment #1 from Michael Müller michael@fds-team.de --- The build system does not generate source packages for Debian / Ubuntu and instead directly compiles the binary package. The scripts that are run inside of the virtual machines to build the packages are available at https://github.com/wine-compholio/wine-packaging. So you got everything you need to rebuild the packages in the same way as done on our build server. This does not imply that this method is the same as you would do it locally on your machine.
Btw, I am also pretty sure that publishing the build files is not a requirement of the LGPL. You have to provide the source code for the compiled binary files, which is obviously done as all packages use an unpatched version of the corresponding wine source code. However, you are not required to tell someone how you build it. The LGPL only requires you to publish modifications of the original source code, but the build files are not part of it. We could even link against something proprietary during the build and this would still be fine. The LGPL allows linking against non LGPL code, as long as the LGPL part can be replaced with a self compiled version.