refactor(entrypoint.sh): use IFS="," for ... instead of jq and while loop

Signed-off-by: Vojtěch Mareš <vojtech@mares.cz>

Dockerfile

@@ -1,6 +1,6 @@
 FROM alpine:3.22
 
-RUN apk add --no-cache ca-certificates cosign jq
+RUN apk add --no-cache ca-certificates cosign
 
 COPY entrypoint.sh /entrypoint.sh
 

entrypoint.sh

@@ -5,17 +5,7 @@ if [ -z ${PLUGIN_IMAGES+x} ]; then
     exit 1
 fi
 
-echo "==== DEBUG ===="
-echo "${PLUGIN_IMAGES}"
-echo
-echo "jq '.'"
-echo "${PLUGIN_IMAGES}" | jq '.'
-echo
-echo "jq '.[]'"
-echo "${PLUGIN_IMAGES}" | jq '.[]'
-echo
-echo "==== DEBUG ===="
-
-echo "${PLUGIN_IMAGES}" | jq --raw-output '.[]' | while read -r image; do
+IFS=","
+for image in ${IMAGES}; do
     cosign sign --key "${PLUGIN_KEY_PATH:-"./cosign.key"}" "${image}"
 done