Fix leaking globals on Windows #1870

Job	Run time
specs (ubuntu, 3.0.6)	1m 32s
RuboCop	32s
specs (ubuntu, 3.1.4)	1m 36s
specs (ubuntu, 3.2.2)	1m 31s
specs (ubuntu, 3.3.0)	1m 29s
specs (macos, 3.0.6)	2m 0s
specs (macos, 3.1.4)	1m 31s
specs (macos, 3.2.2)	1m 40s
specs (macos, 3.3.0)	1m 28s
specs (windows, 3.0.6)	4m 42s
specs (windows, 3.1.4)	4m 25s
specs (windows, 3.2.2)	4m 30s
specs (windows, 3.3.0)	3m 40s
specs (ubuntu, 3.3.0, --enable-frozen-string-literal)	1m 26s
	32m 2s

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