Distribute image build across multiple runners #245

Job	Run time
Fetch NGINX mainline version	3s
Fetch NGINX mainline version	3s
Fetch NGINX mainline version	3s
Build Alpine NGINX mainline slim Docker image (linux/amd64)	55s
Build Alpine NGINX mainline slim Docker image (linux/amd64)	55s
Build Alpine NGINX mainline slim Docker image (linux/amd64)	20s
Build Alpine NGINX mainline slim Docker image (linux/arm/v6)	15m 11s
Build Alpine NGINX mainline slim Docker image (linux/arm/v6)	15m 11s
Build Alpine NGINX mainline slim Docker image (linux/arm/v6)	15m 47s
Build Alpine NGINX mainline slim Docker image (linux/arm/v7)	15m 53s
Build Alpine NGINX mainline slim Docker image (linux/arm/v7)	15m 53s
Build Alpine NGINX mainline slim Docker image (linux/arm/v7)	16m 0s
Build Alpine NGINX mainline slim Docker image (linux/arm64)	38s
Build Alpine NGINX mainline slim Docker image (linux/arm64)	38s
Build Alpine NGINX mainline slim Docker image (linux/arm64)	38s
Build Alpine NGINX mainline slim Docker image (linux/386)	1m 59s
Build Alpine NGINX mainline slim Docker image (linux/386)	1m 59s
Build Alpine NGINX mainline slim Docker image (linux/386)	1m 52s
Build Alpine NGINX mainline slim Docker image (linux/ppc64le)	1m 1s
Build Alpine NGINX mainline slim Docker image (linux/ppc64le)	15m 34s
Build Alpine NGINX mainline slim Docker image (linux/ppc64le)	15m 43s
Build Alpine NGINX mainline slim Docker image (linux/s390x)	2m 29s
Build Alpine NGINX mainline slim Docker image (linux/s390x)	15m 14s
Build Alpine NGINX mainline slim Docker image (linux/s390x)	15m 26s
merge	0s
merge	12s
merge	9s
	2h 49m 46s

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