package/gcc: backport PR56780 patches

--disable-install-libiberty configure option is broken
in gcc 4.8.x, so libiberty.a is always installed in HOST_DIR.

This library broke the host-gdb build due to a fpic/fPIC issue.

Fixes:
http://autobuild.buildroot.net/results/28f/28f3074e99a35f4321dad2fa6c5abdad14d2d2c6/



And many more.

Signed-off-by: Romain Naour <romain.naour@openwide.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>