fix: correctly handle multi-line tag digests output

kaniko outputs each tag on a new line, so users that push multiple tags
at once would get an error as the output wasn't prepared to handle multi-line
text

Dockerfile

@@ -2,7 +2,7 @@ FROM alpine as certs
 
 RUN apk --update add ca-certificates
 
-FROM gcr.io/kaniko-project/executor:v1.20.0-debug
+FROM gcr.io/kaniko-project/executor:v1.21.1-debug
 
 SHELL ["/busybox/sh", "-c"]
 

entrypoint.sh

@@ -94,13 +94,17 @@ EOF
 # https://github.com/GoogleContainerTools/kaniko/issues/1803
 # https://github.com/GoogleContainerTools/kaniko/issues/1349
 export IFS=''
+# Removes a trailing new line
+ARGS=$(echo "${ARGS}" | sed 's/\n*$//')
 kaniko_cmd="/kaniko/executor ${ARGS} --reproducible --force"
 echo "Running kaniko command ${kaniko_cmd}"
 eval "${kaniko_cmd}"
 
 echo "image=$IMAGE" >> "$GITHUB_OUTPUT"
 echo "digest=$(cat /kaniko/digest)" >> "$GITHUB_OUTPUT"
-echo "image-tag-digest=$(cat /kaniko/image-tag-digest)" >> "$GITHUB_OUTPUT"
+echo "image-tag-digest<<EOF" >>"$GITHUB_OUTPUT"
+echo "$(cat /kaniko/image-tag-digest)" >>"$GITHUB_OUTPUT"
+echo 'EOF' >>"$GITHUB_OUTPUT"
 
 
 if [ -n "$INPUT_SKIP_UNCHANGED_DIGEST" ]; then