test_runner: fix memory leaks in runner #2379

Job	Run time
Build slim tarball	1m 31s
aarch64-linux: with shared libraries	22m 19s
aarch64-darwin: with shared libraries	30m 35s
x86_64-darwin: with shared libraries	44m 30s
x86_64-linux: with shared libraries	27m 30s
	2h 6m 25s

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