KCFLAGS?

[abfipes12]

you know that kernel uses KCFLAGS (and CFLAGS will workn't)?
also ... you dont "flto" for linux lto but you need make with LLVM=1 (compile kernel with clang and other llvm programs) and then try to find and check CONFIG_LTO_CLANG_FULL or CONFIG_LTO_CLANG_THIN. (that is no lto with gcc (officially)).

some random linux lore
suggests that -falign-functions=64 is worth trying.

and this dated phoronix post
says that clang + lto not bad.

to conclude, install llvm and try:
make LLVM=1 KCFLAGS="-O3 -march=native -falign-functions=64 -pipe"

or just install clear linux kernel ... or clear linux, or gentoo high on rice