LGPL-only LibVLC CI builds for all platforms

I think it would be beneficial to have official CI builds for LibVLC that are compliant with the LGPL license, since this is how LibVLC is advertised, an LGPL v2.1 licensed library.

Currently, many LibVLC users from various languages usually use a GPLv2.1 build unknowingly and fail to respect the license, since we do not provide ready-to-use LGPL2.1 builds, and yet we advertise LibVLC as a library under the LGPL.

This would involve either:

• building with --disable-gpl --disable-gnuv3,
• building libvlc as normal, and removing all the non-lgpl2.1 binaries at the packaging step.

Bonus: It would be nice to make sure that all tests still pass when removing every non-compliant module and contrib.

Our CI servers seem quite busy already, so I could see that as being an issue.