Add kernel.mk for inline kernel building

Change-Id: I2c4c4506aee3a242671b39fdc17d54fa6673cc04
Add optimization paramater to lunch

When you run lunch you can see the optimizations enabled in your boradconfig.mk
Current options are TARGET_GCC_VERSION/TARGET_USE_O3/TARGET_USE_LINARO_STRING_ROUTINES

Change-Id: Ie2870165906129381fdc0c28fc13f26fbb11c22d
improve ccache support

Change-Id: I5401f7068d6f830adba293eadbbe307e6bf736f8