Add building with kernel helper scripts

This scripts are for building GSI targets with prebuilt kernel
binaries. The kernel binaries are from a kernel build on AndroidCI,
or the build chaining on build server.

download_kernels_prebults.sh
  For local testing the build chaining with kernel prebuilt binaries.
  Downloads the kernel prebuilts binaries from AndroidCI with the
  build ID in the file `bid`.

kernel_info_to_dist.sh
  A postprocessing script to download the kernel prebuilt binaries
  and debugging information from AndroidCI, and output to dist folder.

repack_kernel(_x86_64).sh
  The preprocessing helper scripts for build chaining with kernel
  prebuilt binaries.

Bug: 196916063
Test: na
Change-Id: I081585d20f8d4a4e3cf135a1447775a8562d6fae
5 files changed