buildman: Enable buildman on aarch64 hosts

At kernel.org aarch64 toolchains are published in folder
arm64. Fix the URL for that case, so that we can fetch
toolchains on aarch64 machines.

Signed-off-by: Matthias Brugger <mbrugger@suse.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
1 file changed