scripts/ext-tools: introduce new script to install prebuilt tools

scripts/ext-tools: introduce new script to install prebuilt tools

Add a simple script to make it easier to install a prebuilt tools tar.
Currently it will be used by our tools container and kernel workflow on
github.

Simple script that take a tar that contains prebuilt host tools, extract
them and refresh the timestamps to skip recompilation of such host
tools.

By default it refresh timestamps of build_dir/host and
staging_dir/host/stamp.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>