Nothing uses $(LDFLAGS_plugin) anywhere.

Ref #9022

As reported on Reddit

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

This change will make the transition easier between the previously released
installer (that doesn't remember user choices) and this one. Without it the
old installer would fall back to the "Recommended" preset.

This allows updates without user intervention.

In case of upgrade, most pages will be skipped in favor of a smoother and faster upgrade.