Provide default user / group IDs for alma9 rpmbuild docker

This is required for better compatibility with host platforms where
the active uid (from id -u) might conflict with the base image system
user ids.

We chose 1000 as something outside the standard uid range, and
conveniently the default uid on Ubuntu systems, ref:
https://refspecs.linuxfoundation.org/LSB_3.0.0/LSB-Core-generic/LSB-Core-generic/uidrange.html

I've also changed the Dockerfile to pick up the TARGETARCH value so
that we get the right bazelisk executable.

Author: wade-arista

contrib/alma9_rpmbuild_docker/docker/Dockerfile

@@ -1,10 +1,11 @@
 FROM almalinux:9.6
 
-ARG USER_ID
-ARG GROUP_ID
+ARG USER_ID=1000
+ARG GROUP_ID=1000
+ARG TARGETARCH
 
 ENV BAZELISK_VERSION=v1.26.0
-ENV BAZELISK_URL=https://github.com/bazelbuild/bazelisk/releases/download/${BAZELISK_VERSION}/bazelisk-linux-amd64
+ENV BAZELISK_URL=https://github.com/bazelbuild/bazelisk/releases/download/${BAZELISK_VERSION}/bazelisk-linux-${TARGETARCH}
 
 RUN dnf install -y \
     ca-certificates \

contrib/alma9_rpmbuild_docker/run.sh

@@ -21,7 +21,12 @@ volume="${VOLUME:-bazel-cache}"
 dir=$(realpath "$(dirname "$0")")
 repo_root="$dir/../.."
 
-docker build -t "$tag" --build-arg USER_ID="$(id -u)" --build-arg GROUP_ID="$(id -g)" "$dir/docker"
+USER_ID=${USER_ID:-1000}
+GROUP_ID=${GROUP_ID:-1000}
+(
+   set -x
+   docker build -t "$tag" --build-arg USER_ID="$USER_ID" --build-arg GROUP_ID="$GROUP_ID" "$dir/docker"
+)
 
 docker_args=(
    -v "$volume":/home/devuser/.cache
@@ -31,4 +36,7 @@ docker_args=(
    -i
    -t
 )
-exec docker run "${docker_args[@]}" "$tag" "$@"
+(
+   set -x
+   exec docker run "${docker_args[@]}" "$tag" "$@"
+)