I was having the same issue while using an JDK Alpine image in the Build stage, and solve it by changing it to a regular JDK image, I was able to generate my docker container even with the ${os.detected.classifier} in the POM.

from:

FROM maven:3.9.9-eclipse-temurin-21-alpine AS builder

to:

FROM maven:3.9.9-eclipse-temurin-21 AS builder

the same image that is used in the project repository:
https://github.com/chrisblakely01/java-spring-microservices/blob/main/billing-service/Dockerfile

for anyone interested this is the project course video
https://www.youtube.com/watch?v=tseqdcFfTUY by Chris Blakely,
awesome course.