Vulkan: SPIR-V Gen: Support break and continue This is simply done by issuing a branch to the merge or continue blocks respectively. Bug: angleproject:4889 Change-Id: I3e96a3b0f1a0533aa4eac519ab64a87600c0983b Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2957810 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Tim Van Patten <timvp@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>