Out-Of-Tree kernel build scripts

Or "out-of-tree", as these are still in a way dependent on the Android build tree. But paths can easily be changed and the relevant tools cloned/copied/installed without AOSP tree.

These scripts build the Sony Open Devices kernel outside of the tree and generate a boot.img as well as a dtbo.img. It saves a tremendous amount of time since the AOSP build system easily takes 15-20 seconds to read makefiles, decides it doesn't need to regenerate them, call mkbootimg and deliver the boot.img. Calling this tool outside of the build results in much quicker iteration.

Currently the path to the compilers, ramdisks and kernels are hardcoded, but easy to change.

Usage:

1. Clone directly in the root of an AOSP tree (or point the ANDROID_BUILD_TOP environment variable to this root);
2. Call ./oot/oot.sh <device name> (use -h to see more options);
3. Flash the images. For simplicity, you can also add the -f option to the command, that will flash and fastboot reboot the device after building.

TODO:

• Expand platforms passed to this script (ie. passing kumano builds griffin and bahamut);
• Options to specify alternate ramdisk and kernel directory?