cl_khr_kernel_clock: use create_single_kernel_helper (KhronosGroup#1978)

`create_single_kernel_helper` invokes `clBuildProgram` and sets
`-cl-std` to the latest version supported by the context.

The vast majority of tests are using `create_single_kernel_helper`
instead of the `..._create_program` variant, so use the former for the
sake of consistency.

---------

Signed-off-by: Sven van Haastregt <sven.vanhaastregt@arm.com>

test_conformance/extensions/cl_khr_kernel_clock/kernel_clock.cpp

@@ -109,21 +109,14 @@ class KernelClockTest {
 
  ptr = kernel_src;
 
- error = create_single_kernel_helper_create_program(
- context, &program, 1, &ptr);
+ error = create_single_kernel_helper(context, &program, &kernel, 1,
+  &ptr, "SampleClock");
  test_error(error, "Failed to create program with source");
 
- error =
- clBuildProgram(program, 1, &device, nullptr, nullptr, nullptr);
- test_error(error, "Failed to build program");
-
  out_mem = clCreateBuffer(context, CL_MEM_WRITE_ONLY,
  sizeof(cl_uint), nullptr, &error);
  test_error(error, "clCreateBuffer failed");
 
- kernel = clCreateKernel(program, "SampleClock", &error);
- test_error(error, "Failed to create kernel");
-
  error = clSetKernelArg(kernel, 0, sizeof(out_mem), &out_mem);
  test_error(error, "clSetKernelArg failed");