BB: binutils: link libbfd and libopcodes dynamically again

Backport of r42337.

Signed-off-by: Jonas Gorski <jogo@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/branches/barrier_breaker@42338 3c298f89-4303-0410-b956-a3cf2f4a3e73
Merge branch 'master' of git://git.openwrt.org/14.07/openwrt