Modernize sources list for containerized package manager

installJRMC

@@ -434,12 +434,17 @@ get_latest_mc_version() {
   # Use generalized containerized package manager to determine latest MC version
   if install_package --silent buildah && 
   cnt=$(buildah from --quiet alpine:edge 2>/dev/null) &&
-  buildah run "$cnt" -- sh -c "apk add apt &>/dev/null && tee /etc/apt/sources.list.d/jriver.sources <<EOF
+  buildah run "$cnt" -- sh -c '
+apk add apt &>/dev/null
+cat <<EOF > /etc/apt/sources.list.d/jriver.sources
 Types: deb
 URIs: https://dist.jriver.com/latest/mediacenter/
-Suites: $1
+Suites: '"$1"'
 Components: main
-EOF ; cat /etc/apt/sources.list.d/jriver.sources; apt update --allow-insecure-repositories" &&
+EOF
+cat /etc/apt/sources.list.d/jriver.sources
+apt update --allow-insecure-repositories
+' &&
   MC_VERSION=$(buildah run "$cnt" -- apt-cache policy mediacenter?? | grep Candidate | awk '{print $2}' | sort -V | tail -n1) &>/dev/null &&
   [[ $MC_VERSION =~ ^[0-9]+\.[0-9]+\.[0-9]+ ]]; then
     mc_version_source="containerized package manager"