opencl: fix build targeting CL 2 (#16554)

Author: lhez

ggml/src/ggml-opencl/ggml-opencl.cpp

@@ -2348,8 +2348,13 @@ static ggml_backend_opencl_context * ggml_cl2_init(ggml_backend_dev_t dev) {
         svm_caps & CL_DEVICE_SVM_ATOMICS ? "true" : "false");
 
     if (opencl_c_version.major >= 3) {
+        // Assume it is not available for 3.0, since it is optional in 3.0.
+        // If compiling against 3.0, then we can query.
+        backend_ctx->non_uniform_workgroups = false;
+#if CL_TARGET_OPENCL_VERSION >= 300
         CL_CHECK(clGetDeviceInfo(device, CL_DEVICE_NON_UNIFORM_WORK_GROUP_SUPPORT, sizeof(cl_bool),
                                  &backend_ctx->non_uniform_workgroups, 0));
+#endif
     } else {
         GGML_ASSERT(opencl_c_version.major == 2);
         // Non-uniform workgroup sizes is mandatory feature in v2.x.