Fix windows compatibility regression of task `dir` key #1813

Job	Run time
run-determination	3s
check-outdated (ruledocsgen)	20s
check-config (.)	20s
check-style (.)	23s
check-outdated (docsgen)	15s
check-errors (docsgen)	46s
check-style (ruledocsgen)	28s
check-style (docsgen)	23s
check-outdated (.)	18s
check-errors (.)	45s
check-errors (ruledocsgen)	49s
check-formatting (ruledocsgen)	15s
check-formatting (.)	15s
check-config (ruledocsgen)	25s
check-config (docsgen)	23s
check-formatting (docsgen)	15s
	6m 23s

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