try this

Author: gdams

linux/jdk/alpine/src/main/packaging/Dockerfile

@@ -31,6 +31,7 @@ RUN --mount=type=secret,id=gpg,gid=1000,uid=1000,dst=/tmp/private.rsa \
 		wget -o /home/builder/.abuild/private.rsa.pub https://packages.adoptium.net/artifactory/api/security/keypair/public/repositories/apk; \
 	else \
 		abuild-keygen -a -n; \
+		sudo cp /home/builder/.abuild/*.rsa.pub /etc/apk/keys/; \
 	fi
 
 # Prepare entrypoint