Makefile: build optimizations
From a number of sources. A couple of the more specific ones:
-graphite (temasek)
-fix for GCC 4.8 (Wootever via temasek)
-L1/L2 cache size (JustArchi via arter97)
-Fixed CROSS_COMPILE path (build fails if it starts with ~/ instead of
/home/<user>)
-Added -fno-associative-math to net/netfilter
	--fassociative-math (from -funsafe-math-optimizations) causes a
	 segmentation fault with this toolchain. We can probably remove
	 it in the future.
repo: update build script
-fixed the dbttool path
-added ENABLE_GRAPHITE=true to the make command line