gcc: enable ld.gold and ld.bfd (default)

GCC 4.8 allows both linkers available, and default can be changed
by passing -fuse-ld={gold,bfd} option to the driver.

Signed-off-by: David Abdurachmanov <davidlt@cern.ch>
gcc: bump binutils version to 2.23.2

Signed-off-by: David Abdurachmanov <davidlt@cern.ch>