ci: publish-client: Use Linux arch name

The `ARCH` environment varible set by the Jenkins pipeline uses the
Kubernetes names for CPU architectures.  RPMs use the Linux kernel
names, which are not the same.  Using the former, therefore, in the
`include` filter for `rsync` results in no packages being uploaded to
the repository.

ci/publish-client.sh

@@ -1,12 +1,13 @@
 #!/bin/sh
 
+ARCH="$(uname -m)"
 REPO_HOST=jenkins@files.pyrocufflink.blue
 REPO_PATH=/srv/www/repohost/repos/dch/fedora/$(rpm --eval %fedora)
 
 ssh-add -l
 ssh-add -L
 
-case "$(uname -m)" in
+case "${ARCH}" in
 x86_64)
     # only include the SRPM once
     include='*.rpm'