[1.11>master] [MERGE #6009 @MikeHolman] disable switch opt when breaking out of loops

Merge pull request #6009 from MikeHolman:switchbug1_11

Cherry-picking to release/1.11 from master.

Switch opt gets confused when we need to branch to labels outside the loop, so just disabling it in this case.
Fixes #5985

Author: MikeHolman