test: improve WPT runner summary #5243

Job	Run time
Build slim tarball	2m 5s
x86_64-linux: with shared libraries	21m 53s
x86_64-darwin: with shared libraries	28m 46s
aarch64-darwin: with shared libraries	22m 22s
aarch64-linux: with shared libraries	18m 44s
	1h 33m 50s

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