bionic-amd64-tf-m-build: Switch to use armclang's from S3 bucket

Arm Clang toolchains are no longer accessible via straight HTTP requests.
Instead, they are mirrored to an S3 bucket, files from which are made
available to build.sh, which in turn makes them available to Dockerfile.

This is similar to changes previously made to TF-A images.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: Iebf0b1089d1963bac8aa8b49621540741762183f
3 files changed