Convert absolute paths used in `ci:validate` task to Windows format #1335

Job	Run time
run-determination	1s
check-config (./)	23s
check-errors (./)	32s
check-config (docsgen)	17s
check-errors (docsgen)	33s
check-config (ruledocsgen)	19s
check-errors (ruledocsgen)	33s
check-formatting (./)	16s
check-formatting (docsgen)	16s
check-outdated (./)	20s
check-style (./)	17s
check-formatting (ruledocsgen)	21s
check-outdated (docsgen)	16s
check-style (docsgen)	22s
check-outdated (ruledocsgen)	17s
check-style (ruledocsgen)	14s
	5m 17s

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