ST: Use clock_gettime to prevent time jumping backwards. v7.0.17 #3622

Job	Run time
cygwin64-cache	1m 54s
utest-regression-blackbox-test	9m 37s
multiple-arch-aarch64	23m 53s
multiple-arch-armv7	22m 5s
fast	1s
cygwin64	15m 2s
build-ubuntu16	3m 31s
build-ubuntu20	3m 46s
build-centos7	5m 1s
build-ubuntu18	3m 5s
build-cross-aarch64	5m 16s
build-cross-arm	5m 12s
coverage	4m 3s
multiple-arch-amd64	3m 3s
test-done	1s
	1h 45m 30s

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