add flavor to build-docker workflow #29

Job	Run time
create-release	6s
create-release	6s
Build Release Docker image	0s
Build Release Docker image	0s
Build Pre-release Docker image / build-docker (arm64)	1s
Build Pre-release Docker image / build-docker (arm64)	10m 20s
Build Pre-release Docker image / build-docker (amd64)	30s
Build Pre-release Docker image / build-docker (amd64)	6m 52s
Build Pre-release Docker image / build-docker (arm/v7)	11s
Build Pre-release Docker image / build-docker (arm/v7)	10m 16s
build-binaries (linux)	40s
build-binaries (linux)	2m 25s
build-binaries (linux-arm64)	2m 21s
build-binaries (linux-arm64)	2m 21s
build-binaries (freebsd)	17s
build-binaries (freebsd)	2m 53s
Build Pre-release Docker image / docker-manifest	0s
Build Pre-release Docker image / docker-manifest	30s
	39m 49s

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