dockerfiles: Add support for s390x #8240

Job	Run time
run-ubuntu-unit-tests (-DFLB_JEMALLOC=On, gcc)	19m 54s
run-ubuntu-unit-tests (-DFLB_JEMALLOC=On, clang)	19m 40s
run-ubuntu-unit-tests (-DFLB_JEMALLOC=Off, gcc)	18m 53s
run-ubuntu-unit-tests (-DFLB_JEMALLOC=Off, clang)	17m 50s
run-ubuntu-unit-tests (-DFLB_SMALL=On, gcc)	18m 17s
run-ubuntu-unit-tests (-DFLB_SMALL=On, clang)	20m 31s
run-ubuntu-unit-tests (-DSANITIZE_ADDRESS=On, gcc)	18m 48s
run-ubuntu-unit-tests (-DSANITIZE_ADDRESS=On, clang)	19m 31s
run-ubuntu-unit-tests (-DSANITIZE_UNDEFINED=On, gcc)	18m 56s
run-ubuntu-unit-tests (-DSANITIZE_UNDEFINED=On, clang)	18m 52s
run-ubuntu-unit-tests (-DFLB_COVERAGE=On, gcc)	53m 34s
run-ubuntu-unit-tests (-DFLB_SANITIZE_MEMORY=On, gcc)	18m 58s
run-ubuntu-unit-tests (-DFLB_SANITIZE_MEMORY=On, clang)	18m 29s
run-ubuntu-unit-tests (-DFLB_SANITIZE_THREAD=On, gcc)	19m 18s
run-ubuntu-unit-tests (-DFLB_SANITIZE_THREAD=On, clang)	18m 56s
run-macos-unit-tests (-DFLB_JEMALLOC=Off)	9m 57s
run-macos-unit-tests (-DFLB_SANITIZE_MEMORY=On)	9m 54s
run-macos-unit-tests (-DFLB_SANITIZE_THREAD=On)	11m 6s
Unit tests (matrix)	1s
	5h 51m 25s

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