Revert "Makefile: -O3 optimization flags"

This reverts commit d20d9e41862397b2ecfce7013aa8f43a26c4cd84.
update boot.img
Revert "frandom: enable frandom in configs"

This reverts commit c41c898672a518ef4c975fee877d6930b51f90b0.
build script: update linaro toolchain
update nebula to v2.1