Fix url for buildcaches (#271)

docker/Dockerfile

@@ -1,7 +1,6 @@
 FROM ubuntu:22.04 AS stage
 
-ENV DEBIAN_FRONTEND=noninteractive \
-    REMOTE_BUILDCACHE_URL="s3://spack-binaries/releases/v0.21/tutorial"
+ENV DEBIAN_FRONTEND=noninteractive
 
 # Install AWS cli
 RUN apt-get update -y && \
@@ -16,24 +15,22 @@ RUN curl "https://awscli.amazonaws.com/awscli-exe-linux-x86_64.zip" -o "awscliv2
 
 # Download the buildcache 
 RUN mkdir /mirror
-RUN aws --region us-east-1 --no-sign-request s3 sync s3://spack-binaries/releases/v0.20/tutorial /mirror
+RUN aws --region us-east-1 --no-sign-request s3 sync s3://spack-binaries/releases/v0.21/tutorial /mirror
 RUN rm -rf /mirror/buid_cache/_pgp
 # TODO: Get the keys from aws as soon as they're fixed
 # RUN aws --region us-east-1 --no-sign-request s3 sync s3://spack-binaries/releases/v0.20/build_cache/_pgp /mirror/build_cache/_pgp
 COPY tutorial.pub /mirror/build_cache/_pgp/78F3726939CA1B94893B66E8BC86F6FB94429164.pub
 
 FROM ghcr.io/spack/tutorial-ubuntu-22.04:latest
 
-ENV DEBIAN_FRONTEND=noninteractive
-
 COPY --from=stage /mirror /mirror
 RUN chmod -R go+r /mirror
 
 COPY /packages.yaml /etc/spack/packages.yaml
 COPY /config.yaml /etc/spack/config.yaml
 COPY /concretizer.yaml /etc/spack/concretizer.yaml
 
-RUN apt-get remove -y gcc-12 && \
+RUN DEBIAN_FRONTEND=noninteractive apt-get remove -y gcc-12 && \
     apt-get update -y && \
     apt-get install -y --no-install-recommends emacs bash-completion less && \
     apt-get -y autoremove --purge && \