Test

Use ubuntu20, --build-cache=off, --ffmpeg-opus=off #207

Job	Run time
multiple-arch-aarch64	5m 42s
cygwin64-cache	2m 47s
multiple-arch-armv7	5m 40s
utest-regression-blackbox-test	7m 11s
fast	1s
cygwin64	10m 47s
build-ubuntu20	1m 41s
build-cross-arm	4m 3s
build-centos7	2m 15s
build-cross-aarch64	2m 25s
build-ubuntu16	2m 43s
build-ubuntu18	2m 46s
coverage	3m 50s
multiple-arch-amd64	2m 15s
test-done	2s
	54m 8s

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