This commit adds an optional dependency to libsqlite3-sys to provide a
bundled version of libsqlite3 as well instead of relying on a system
provided version. Also use the `link_cplusplus` crate to handling
linking libc++ for us.

Instead we now just check if it was build from source (by checking the
relevant environment variables) and if that was the case we link that
version statically.

Co-authored-by: Michael Kirk <michael.code@endoftheworl.de>