fix(@angular-devkit/core): handle Windows drive letter case insensiti… #282

Job	Run time
list	37s
workflow (build-cli)	2m 2s
workflow (modules-builder-tests)	2m 29s
workflow (devkit-core-tests)	1m 48s
workflow (devkit-core-tests-rerun)	1m 59s
workflow (build-unit-tests)	2m 30s
	11m 25s

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