Bug 670659 added a check to see whether --gc-sections harms the debugging experience. The check relies on the presence of the .debug_ranges section in the compiled code. However, it appears that -g with GCC 4.8 doesn't even produce .debug_ranges, but .debug_aranges, which I presume is more efficient. The check should be made more robust.
(It turns out too that older versions of binutils don't necessarily understand the debugging output by newer versions of GCC, which can neuter the check, but I think we can leave that as caveat user, since the distros should be distributing compatible versions of everything.)