makefile: compile with ccache

Change-Id: I98a5afa36c1f2a47f7b0ea7f53d64929620b30eb
makefile: add optimisation options in kconfig

-o3, -o2 or -os

lto, graphite, ofastmath

Change-Id: I50b0b0896827e8aae4da5f7e3b6c3cd5050c0577