libbcc: Fix build with gcc 4.8+

gcc 4.8+ exports __ashldi3, __divsi3, __fixdfdi, ... in libgcc.
Redefining them here causes linker errors.

Change-Id: I21e17608bc7ec0b13d56602c1169a2aaec121fcf
Signed-off-by: Bernhard Rosenkränzer <Bernhard.Rosenkranzer@linaro.org>

Conflicts:
	runtime/lib/ashldi3.c
	runtime/lib/lshrdi3.c