Merge pull request #1123 from herwinw/kernel_caller #1661

Job	Run time
RuboCop	27s
specs (ubuntu, 3.0.6)	1m 28s
specs (ubuntu, 3.1.4)	1m 33s
specs (ubuntu, 3.2.2)	1m 23s
specs (ubuntu, 3.3.0)	1m 23s
specs (macos, 3.0.6)	1m 24s
specs (macos, 3.1.4)	1m 39s
specs (macos, 3.2.2)	1m 9s
specs (macos, 3.3.0)	1m 21s
specs (windows, 3.0.6)	3m 32s
specs (windows, 3.1.4)	4m 12s
specs (windows, 3.2.2)	5m 36s
specs (windows, 3.3.0)	4m 27s
specs (ubuntu, 3.3.0, --enable-frozen-string-literal)	1m 25s
	30m 59s

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