Rollup merge of #74598 - mzohreva:mz/fix-test, r=KodrAus
Rollup merge of #74598 - mzohreva:mz/fix-test, r=KodrAus

Fix sync_once_cell_does_not_leak_partially_constructed_boxes

Spinning multiple threads in this test causes a deadlock in
SGX where thread scheduling is not preemptive.

cc @jethrogb @AdrianCX

graydon/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust