Revert "add new optimization level option (gcc4.6)"

This reverts commit a02b5eb7a151a18caff0a56bd5f70a0f9b9247ce.
Revert "lib: avoid ICE on linaro 8.12"

This reverts commit 6f879bf8cfcf3c886a2cc2d39b99fab334f07fea.
Revert "Makefile: adding config variable for Os/O2/O3 compilation"

This reverts commit 252b684b829ff91181c898e5e5dfb2bef3fbb452.
Makefile: Added ARM optimizations