If a loop has only one break case, Metal appears to re-order it to after
the loop ends, which goes against the expected behavior for reconvergence.
Work around this by putting the break statement into a trivial, always-true
runtime conditional, when maximal reconvergence is requested.
Fixes dEQP-VK.reconvergence.maximal.compute.nesting*
Reviewed-by: Arcady Goldmints-Orlov <arcady@lunarg.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/41229>