[GOLD] Fix spurious "plugin needed to handle lto object" warnings
lto_slim_object_ was unitialized. I also thought it worth adding a sanity check on the .gnu.lto_.lto.* section size, and made some other tidies. PR 24768 * layout.cc (Layout::Layout): Init lto_slim_object_. * object.cc (Sized_relobj_file::do_layout): Wrap overlong line. Don't use C cast. Validate section size. Don't copy contents.