Makefile: tweaks
- Removed hardcoded toolchain.
- -o3 & Cortex-A15 optimizations.
- Enabled ccache

Signed-off-by: LaboDJ <jacopolabardi@gmail.com>

Conflicts:
	Makefile

Conflicts:

	Makefile
vfp: Cortex-A15 optimizations

Signed-off-by: LaboDJ <jacopolabardi@gmail.com>
arm: Cortex-A15 optimizations

Signed-off-by: LaboDJ <jacopolabardi@gmail.com>