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Don't crash when running `cargo profdata --help` #212

Job	Run time
ci (stable, ubuntu-latest, false)	28s
ci (1.70.0, macos-latest, false)	28s
ci (stable, windows-latest, false)	59s
ci (1.70.0, windows-latest, false)	1m 20s
ci (1.70.0, ubuntu-latest, false)	28s
ci (nightly, ubuntu-latest, true)	25s
ci (stable, macos-latest, false)	28s
conclusion	3s
	4m 39s