[Bug other/59893] Use LTO for libgcc.a, libstdc++.a, etc

[d.g.gorbachev at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59893

--- Comment #7 from Dmitry Gorbachev <d.g.gorbachev at gmail dot com> ---
I used to build GCC 4.8/4.9 with -flto in C(XX)FLAGS_FOR_TARGET for quite some
time (both native i686-pc-linux-gnu and a cross), and it seems to work.  I saw
two problems: PR 60160 (for which a patch exists), and PR 59472 (annoying, but
not fatal).