test_runner: add exports option to mock.module #4471

Job	Run time
Build slim tarball	1m 51s
aarch64-linux: with shared libraries	18m 24s
x86_64-linux: with shared libraries	22m 5s
aarch64-darwin: with shared libraries	20m 24s
x86_64-darwin: with shared libraries	42m 16s
	1h 45m 0s

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