Use tini as a zombie process reaper #1295

Job	Run time
test_python_autogen / test_python_autogen	4m 5s
make_boot / make_boot (zynq, PandABox-no-fmc)	1h 7m 20s
make_zpkg / make_zpkg (PandABox-no-fmc)	1h 24m 10s
make_boot / make_boot (zynqmp, xu5_st1-no-fmc)	1h 33m 13s
make_boot / make_boot (zynqmp, PandABrick)	58m 24s
make_zpkg / make_zpkg (PandABox-fmc_24vio)	1h 22m 58s
test_matrix / test_matrix	2m 3s
make_zpkg / make_zpkg (PandABox-fmc_acq427)	1h 34m 26s
make_zpkg / make_zpkg (PandABox-fmc_acq430)	1h 34m 15s
make_zpkg / make_zpkg (PandABox-fmc_lback-sfp_lback)	1h 16m 0s
make_zpkg / make_zpkg (PandABrick)	56m 59s
make_zpkg / make_zpkg (xu5_st1-no-fmc)	38m 57s
make_zpkg / make_zpkg (xu5_st1-fmc_acq430)	1h 18m 37s
test_hdl / test (pcap pgen)	1h 29m 43s
test_hdl / test (seq posenc clock)	47m 43s
test_hdl / test (pcomp lut div bits)	1h 24m 20s
test_hdl / test (counter filter calc)	46m 4s
test_hdl / test (pulse srgate qdec)	51m 16s
release / release	0s
	19h 10m 33s

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