Fix bug when rtc disabled. #1553

Job	Run time
utest-regression-blackbox-test	3m 55s
cygwin64-cache	3m 44s
multiple-arch-aarch64	5m 47s
multiple-arch-armv7	5m 31s
cygwin64	8m 35s
fast	1s
build-ubuntu18	1m 24s
build-centos7	2m 7s
build-cross-arm	2m 18s
build-cross-aarch64	2m 9s
build-ubuntu16	1m 22s
build-ubuntu20	1m 36s
coverage	3m 16s
multiple-arch-amd64	2m 25s
test-done	0s
	44m 10s

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