Prevent zombie processes and properly handle Ctrl+C on bk docker #353

Job	Run time
build (ubuntu-latest, linux, x86-64)	27s
unavailable	25s
id	2m 17s
build (macos-latest, darwin, aarch64)	40s
test (darwin+aarch64)	21s
bottle (xz, darwin+aarch64)	20s
test	21s
audit (ubuntu-latest)	21s
bottle (xz, linux+x86-64)	14s
bottle (gz, darwin+aarch64)	14s
audit (macos-latest)	18s
bottle (gz, linux+x86-64)	13s
	6m 11s

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