test-runner: fix potential memory leaks #1236

Job	Run time
Build slim tarball	1m 34s
x86_64-linux: with shared libraries	34m 57s
x86_64-darwin: with shared libraries	1h 3m 41s
aarch64-linux: with shared libraries	30m 7s
aarch64-darwin: with shared libraries	29m 1s
	2h 39m 20s

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