VCVars: Fix generation if OS is set to WindowsStore #323

Job	Run time
Determine Python versions	1s
Linux test suite / Build Linux container	5s
Windows test suite / Unit & Integration Tests (3.10)	20m 53s
Windows test suite / Functional Tests (3.10)	43m 38s
OSX test suite / Setup and Cache Dependencies	1m 11s
Linux test suite / Docker Runner Tests (3.10)	1m 57s
Linux test suite / Unit Tests (3.10)	1m 57s
Linux test suite / Integration Tests (3.10)	4m 27s
Linux test suite / Functional Tests (3.10)	6m 8s
OSX test suite / Unit Tests (3.10)	1m 5s
OSX test suite / Integration Tests (3.10)	3m 22s
OSX test suite / Functional Tests (3.10)	22m 57s
Code coverage	0s
Deploy to TestPyPI	0s
	1h 47m 41s

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