Used as a sorts of Wrapper to compile a kernel with clang. Needs to be put inside the
Kernel source tree. Only works properly after setup-toolchains.sh has been ran.
Downloads prebuilt UBERTC arm and arm64 gcc 7.0 and AOSP clang toolchains and sets
environment variables that work with build.sh.
The PATHCC variable points towards the toolchains and
the PATHBAK variable is a backup of the PATH variable.