test: improve WPT runner summary #5170

Job	Run time
Build slim tarball	3m 16s
x86_64-darwin: with shared libraries	41m 20s
aarch64-linux: with shared libraries	18m 8s
aarch64-darwin: with shared libraries	20m 38s
x86_64-linux: with shared libraries	21m 41s
	1h 45m 3s

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