cros-build: hana-kevin: Fix depot_tools path
According to the documentation[1], the path should be absolute. This commit fixes an error while using the script under a debian-bullseye system:
depot_tools/bootstrap_python3: line 28: cipd: command not found
depot_tools/bootstrap_python3: line 32: bootstrap-2@3.8.10.chromium.20_bin/python3/bin/python3: No such file or directory
cat: depot_tools/python_bin_reldir.txt: No such file or directory
Signed-off-by: Mylène Josserand mylene.josserand@collabora.com