Use `COPY --link` to share Go layer across OS variants / updates #449

Job	Run time
Generate Jobs	42s
1.22rc1-bookworm	27s
1.22rc1-bullseye	32s
1.22rc1-alpine3.19	30s
1.22rc1-alpine3.18	30s
1.22rc1-windowsservercore-ltsc2022, 1.22rc1-nanoserver-ltsc2022	3m 23s
1.22rc1-windowsservercore-1809, 1.22rc1-nanoserver-1809	3m 27s
1.21.6-bookworm	33s
1.21.6-bullseye	38s
1.21.6-alpine3.19	24s
1.21.6-alpine3.18	23s
1.21.6-windowsservercore-ltsc2022, 1.21.6-nanoserver-ltsc2022	3m 28s
1.21.6-windowsservercore-1809, 1.21.6-nanoserver-1809	3m 25s
1.20.13-bookworm	38s
1.20.13-bullseye	34s
1.20.13-alpine3.19	2m 10s
1.20.13-alpine3.18	2m 9s
1.20.13-windowsservercore-ltsc2022, 1.20.13-nanoserver-ltsc2022	3m 27s
1.20.13-windowsservercore-1809, 1.20.13-nanoserver-1809	3m 25s
1.20.13-bookworm (force build)	2m 24s
1.20.13-bullseye (force build)	2m 26s
1.20.13-alpine3.19 (force build)	2m 6s
1.20.13-alpine3.18 (force build)	2m 13s
1.22rc1-bookworm (i386)	34s
1.22rc1-bullseye (i386)	47s
1.22rc1-alpine3.19 (i386)	30s
1.22rc1-alpine3.18 (i386)	24s
1.21.6-bookworm (i386)	37s
1.21.6-bullseye (i386)	34s
1.21.6-alpine3.19 (i386)	24s
1.21.6-alpine3.18 (i386)	25s
1.20.13-bookworm (i386)	32s
1.20.13-bullseye (i386)	36s
1.20.13-alpine3.19 (i386)	2m 17s
1.20.13-alpine3.18 (i386)	2m 22s
	49m 56s

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