Merge pull request #3148 from github/cklin/just-test_file-serial #5162

Job	Run time
Diagnostic export (macos-latest, nightly-latest)	1m 20s
Diagnostic export (windows-latest, nightly-latest)	2m 34s
Diagnostic export (ubuntu-latest, linked)	1m 2s
Diagnostic export (windows-latest, linked)	3m 35s
Diagnostic export (macos-latest, linked)	1m 26s
Diagnostic export (ubuntu-latest, nightly-latest)	1m 1s
	10m 58s

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