Kokoro: Enable macos CI tests

tests/kokoro/macos/continuous.sh

 #!/bin/bash
 
-# TODO(b/130343040): Stub implementation.
+# Fail on any error.
\ No newline at end of file
+set -e
+# Display commands being run.
+set -x
+
+cd git/SwiftShader
+
+git submodule update --init
+
+mkdir -p build && cd build
+
+if [[ -z "${REACTOR_BACKEND}" ]]; then
+  REACTOR_BACKEND="LLVM"
+fi
+
+cmake .. "-DREACTOR_BACKEND=${REACTOR_BACKEND}"
+make -j$(sysctl -n hw.logicalcpu)
+
+# Run the reactor unit tests.
+./ReactorUnitTests
+
+cd .. # Tests must be run from project root
+
+# Run the OpenGL ES and Vulkan unit tests.
+build/gles-unittests
+
+if [ "${REACTOR_BACKEND}" != "Subzero" ]; then
+  # Currently vulkan does not work with Subzero.
+  build/vk-unittests
+fi