Add step to check if image already exists #174

Job	Run time
build (linux/amd64, ubuntu-24.04, jammy, gcc, 12)	1m 37s
build (linux/amd64, ubuntu-24.04, noble, gcc, 14)	2m 4s
build (linux/amd64, ubuntu-24.04, noble, gcc, 13)	2m 4s
build (linux/amd64, ubuntu-24.04, noble, clang, 17)	2m 21s
build (linux/amd64, ubuntu-24.04, noble, clang, 19)	2m 10s
build (linux/amd64, ubuntu-24.04, noble, clang, 16)	1m 48s
build (linux/arm64, ubuntu-24.04-arm, noble, gcc, 14)	2m 18s
build (linux/arm64, ubuntu-24.04-arm, noble, gcc, 13)	2m 4s
build (linux/arm64, ubuntu-24.04-arm, jammy, gcc, 12)	1m 58s
build (linux/amd64, ubuntu-24.04, noble, clang, 18)	1m 49s
build (linux/arm64, ubuntu-24.04-arm, noble, clang, 16)	2m 2s
build (linux/arm64, ubuntu-24.04-arm, noble, clang, 17)	2m 18s
build (linux/arm64, ubuntu-24.04-arm, noble, clang, 18)	2m 31s
build (linux/arm64, ubuntu-24.04-arm, noble, clang, 19)	2m 13s
merge	-1s
	29m 16s

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