+platforms=${platforms:-}
+# Derive arch from label if it isn't set
+if [ -z "${arch:-}" ] ; then
+ # Labels may be platform specific, eg. jammy-amd64, deb12-armhf
+ regex='[[:alnum:]]+-([[:alnum:]]+)'
+ if [[ "${platforms}" =~ ${regex} ]] ; then
+ arch="${BASH_REMATCH[1]}"
+ else
+ arch="${platforms:-}"
+ fi
+fi