briefly defer yielding the thread/gvl #671

Job	Run time
omnibus compilations, trigger	3s
omnibus compilations, #2	31m 15s
omnibus compilations, #1	28m 25s
omnibus compilations, #3	21m 23s
omnibus compilations, #7	25m 34s
omnibus compilations, #8	26m 39s
omnibus compilations, #4	25m 42s
omnibus compilations, #10	25m 58s
omnibus compilations, #9	26m 52s
omnibus compilations, #5	26m 49s
omnibus compilations, #12	21m 0s
omnibus compilations, #11	25m 54s
omnibus compilations, #6	26m 7s
omnibus compilations, result	2s
	5h 11m 43s

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