Kokoro: Disable Vulkan tests for Subzero.

These currently do not work.

Bug: b/130343040
Change-Id: Ia97b611f44a5a048f324daa236e84e933a2c6b67
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/29033
Presubmit-Ready: Ben Clayton <bclayton@google.com>
Reviewed-by: Chris Forbes <chrisforbes@google.com>
Tested-by: Ben Clayton <bclayton@google.com>
diff --git a/tests/kokoro/gcp_ubuntu/continuous.sh b/tests/kokoro/gcp_ubuntu/continuous.sh
index e889ca3..e56abe1 100644
--- a/tests/kokoro/gcp_ubuntu/continuous.sh
+++ b/tests/kokoro/gcp_ubuntu/continuous.sh
@@ -25,4 +25,8 @@
 
 # Run the OpenGL ES and Vulkan unit tests.
 build/gles-unittests
-build/vk-unittests
+
+if [ "${REACTOR_BACKEND}" != "Subzero" ]; then
+  # Currently vulkan does not work with Subzero.
+  build/vk-unittests
+fi